A shibboleth on Wall Street and life is that we underestimate change.  I've heard it a million times in popular and academic papers. Zarnowitz adduced it in his study of forecasts 50 years ago also. I felt a fast study might be of interest. Do the big changes following big announcements in the early periods tend to continue or reverse. I tested it for 100 of the biggest changes. As usual the popular view is totally off. There is a big tendency for the big rises to be followed by big declines to an inordinate extent and the same reversal tendency for big declines. The study would have to be expanded to be of merit but it's a much better way of quantifying the effect than the subjective studies festering about.

UPDATE: I found 600 article (items) with the tag "underestimating change stock" on google and many of them are very interesting including an article on underestimating earnings announcement price movements and buying straddles to profit, also analysts not taking account of price changes before earnings announcements in making their predictions. But I didn't come across any that examined a large sample with a definite and non-overlappng data set like mine. My study shows that if you take all the important announcements, and look at the change in the first 10 minutes that are big, there is a significant tendency to reversal. I also looked at all the big 10 minute changes around 830 without regard to the announcement and found the same effect. I can say that at least at the microscopic level, with moves of about 0.2% expected, there is a substantial tendency to overestimate the impact of announcements. 

Adam Grimes writes: 

Thank you for that study and the perspective. It makes a lot of sense, and makes me ask a few related questions:

Something I've been wondering about is the claim that markets switch regimes faster now and that markets basically don't trend as well as they used to.

Two thoughts: 1) it's used as justification for the "death" of simple directional strategies… there does seem to be some evidence that we don't have the long trends of the 1980's that gave CTA-style trend following legendary returns for a while, but question 2): why do we assume this is linear? The people who discuss this would have us believe that we look back to the past and see markets that trend and have now fallen into a chaos (perhaps that's overly dramatic) where markets essentially no longer trend. Isn't it also possible this is cyclical, and that we could see more decades of those long, relatively "easy" trends in the future? The assumption is always that it has been driven by electronic trading, more competition, etc… but I wonder. (Always hard to truly understand the drivers… I guess understanding the effect would be enough.)

Not sure how to look at this idea in an objective way. Does this raise any thoughts?

Adam Grimes CIO, Waverly Advisors, LLC

My book: The Art and Science of Technical Analysis

Shane James writes: 

Hi Vic,

I concur with this.

Of note in many of the macro markets is that there is quite an imbalance in the price formation process.

In other words, within the idea of 'conditional heteroskedaticity' or 'volatility clustering' the relatively large moves do tend to occur contemporaneously and the relatively smaller moves also do the same,

The 'imbalance' I refer to above is that- overwhelmingly- the clustering of small moves proves the point more so than the clustering of large moves.

In terms of sign the smaller moves have more persistence than large.

Rocky Humbert writes: 

The money quote in the Forbes article that you cite is, "Find the trend, but don't sweat the details or the timing because you'll always be wrong." There are 4 sub-statements in this sentence. Which of the 4 are you challenging? And bear in mind that your answer must be consistent with your faith in the "Triumph of the Optimists".



This is a must read!: "Randomness and Order". It's about what randomness and order mean in different disciplines.

Stefan Jovanovich writes:

The historian's comments were revealing: "Quantum physics is in a formal sense random – the same electron can be in two places at the same time – whereas my stuff is random in a different way. It reminded me that data are random everywhere. And our job is to turn them into something more coherent, and that's true across all disciplines."

The idea that "history", like physics, could be formally random, that people are not, in fact, "in control" is still a completely radical idea. The only place you find even a hint of that understanding is among the classicist scholars who are now dying off. For them the archives were and are limited enough to be fully known, and enough time had gone by for the grand Whig and Marxist and German historical school generalizations of earlier historians to have been not been proven by the actual evidence. That still left the details of what could be known and inferred from the limited records; from those the classicists (A. R. Burn, to name one) were able to find "coherence". But it was the coherence one finds each day in the responses individuals make to their particular circumstances, not a grand discovery of a lasting pattern.

Of course, with such a view, there could only be individual histories of times and places and people. No wonder Marx remains fundamentally popular. He granted permission for the permanent presumption that the true generalizations are, as the X-Files put it, "out there".

As Professor Wickham puts it, "Historians love to study tiny details; I love to study tiny details too, but I like to put them together. I think that putting-together process is a very important one."




 By the way, I believe it might be a subject of speculation whether  Mr. Simons and his colleagues have found anomalies that they can still exploit as they might be much too big, and there is much too much competition from other humble anomaly seekers.  Yes, as Mr. Harry Browne would say, as described by  the true believer below, their pantheon of geniuses soars on a much higher level of cognition than myself or any of my colleagues or hundreds of followers - but then again superior intelligence isn't everything. And aside from the profitability of market making, as first enumerated by MFM Osborne, it might be difficult to capture anomalies on a systematic basis that the competitors in St. Louis and other small venues might have missed, no matter their profundity.

Anatoly Veltman writes: 

Does this also answer the query as to WHY would Virtu decide to go public?

A true believer writes: 

If there is anything whatsoever to the legion of gambling analogies to markets, market ecology and human endeavor then most of the chips will end up in very few hands.

The Medallion Fund represents the very apogee of human brilliance so applied to financial markets.

What is more likely, that there is something rotten in Denmark? Or that the combined work of pure genius including:

James Simons

Elwyn Berlekamp

Robert Frey

Henry Laufer

Sean Pattison

James Ax

The whole 'European Contingent' - I will not list those names here.

Plus a host of mere 'worker ants' cleaning data, programming testing machines and keeping the lights on.

Might just have come up with the single best group of high capacity strategies ever known.

We should all celebrate this achievement. It represents everything this list is about, surely?

Trying to pick holes in something like this is the equivalent of the Barron's columnist bearing bearish for 30 years on U.S. stocks.

My belief and optimism is based on facts, not some idol worship groupie phenomenon.

anonymous writes:

Is one allowed to agree with both the True Believer and the Chair? What Simons and the others did was pure genius–they used mathematics to identify the consistent anomalies that occur when people buy and sell securities. Those of us who lack their pure brains and mathematical chops marvel at what they have accomplished and have done our best to create a glacially slow mimicry using employment data and their correlation to the business cycle. (They are playing Scarlatti the way Michelangeli did; I am playing chopsticks hitting one key a month.)

But, as Vic notes, the question is whether or not there remain any arbitrage opportunities left now that those anomalies have been examined in such detail for decades by the far greater number of smart people who have come after the folks at Medallion.

Bill Rafter adds: 

Like others, I agree with both the Chair and Shane. The question then is "how much juice is left in the fruit?" As Stefan says, he gets one a month.

I would posit that it is a question of time frame. Certainly the HFT opportunities are gone for us simple folk, and maybe much of the day trading. But there are still anomalies if we are willing to accept less certainty and leave our bets on the table a little longer. After all, realize the prop shops do not want their worker bees to have an overnight position. Which means those of us willing to have such a position will have an automatic edge. As an example, compare the Open to Close returns to the Close to Open returns of certain derivatives. There's an edge, less than it used to be, but still there, and the edge favors the overnight holders.

Also, we simple folk cannot expect to outperform by trading only SPY (or perhaps its overleveraged sisters), the most competitive and liquid of assets. The greatest returns have always been in the least liquid of assets. 

Shane James replies: 

I see no disagreement with the Chair on this thread. As with the Chair, myself, Medallion, DE Shaw, Citadel and all such people interested in trading from all walks of life - we shall continue to look at new angles, different ways of splicing the available information amongst much else. Medallion too will do this. The outcome? Only the shadow knows.

On this next point, the Chair, myself and anyone with half a clue will be in violent agreement - it is always best to be the bookie . The RenTech entity, at the last count when the info was still public, collected 8% management fee and 45% performance fee (I may be off by just a little here).

To use a collection of letters used by my children to describe this: OMG.

It's good the be the king. 

Jim Sogi writes: 

Much of what they have done is computer science not just math. It also has to do with understanding and moving or changing and understanding and exploiting regulations at the exchanges. In a competitive environment, there will always be an edge available somewhere. They change and move, but there is always opportunity in change, the change in others, the rate of change, the unforeseen effects of changes. I think there is opportunity for the slow and small as well. Computers are stuck with their algos. They leave tracks, patterns, singly and as a group. The markets are complex, and no person or computer knows exactly how it works, though they may find opportunities in complexity. There are always effects of effects of effects, unknown to the actor. Waves spread out from every action.



 This chart attempts to characterize the decline in the technology adoption rate in the United States. (I.e quicker adoption of new technologies). One gathers there were many accuracy issues that the researches came up against but still, the negative correlation is likely a reasonable supposition. It does lead one to ponder if some type of 'technological singularity' approaches wherein some interface between carbon based life and 'technology' leads to almost automatic adoption of new technologies. Perhaps in some not too distant future we will approach the asymtote–as it were.

The more luddite interpretation might be that humanity may begin to rebel against technological adoption as the 'improvements' become increasingly marginal.

We shall see.

anonymous writes: 

An alternative explanation is technology diffusion, in which the diffusion time is inversely correlated with the ability to communicate the innovation.

Alston Mabry writes: 

The first thing I think of is how each technology laid the foundation for and accelerated the adoption of the next. Electricity took a long time because there were no wires to begin with.



 How would President Trump and the Dow react if he runs, and if elected?

Shane James writes: 

Reagan, Eastwood, Schwarzenegger…Trump? Why not! 

Stefan Jovanovich writes:

Ronald Reagan was President of a Union in the 1940s; he was, as the journalists put it, "active" in politics for more than two decades before he ran for governor in California. (To this day I find it wonderfully funny that the Brown clan thought that Reagan - the supposed "amateur" - was an easier opponent than William Knowland.)

The comparison with Clint Eastwood is pretty dodgy. Eastwood is a movie star who can green light any project that interests him, and he has had that power for 4 decades. Reagan was a talented actor who never starred in anything with more than a "B" budget and never made any money in Hollywood at all. Unlike Reagan Eastwood has always been a Republican.

As for Trump, he is the Colonel Sanders of contemporary politics–a recognizable name for a brand that is all signs and no voters. 



 One notes the almost 5 year decline in the prices of Maize, Wheat, Soybeans and notably/most importantly, in the price of Rice.

I am often told to pull my head out of my ^%$#% and look at the real world. Well, I look directly at it now and say this: Why are the international food agencies not involved in these markets now (maybe they are?) buying whatever amounts necessary to begin alleviation programs.

They seem more interested in blaming evil speculators when prices are high.

Perhaps Stefan and Jeff could both rightly put me back in my myopic little box and correct my interpretation of the current situation?

Stefan Jovanovich writes: 

I can't, Shane. Your comments are literally a meal for the billion and more who still live have not to mouth. The central banks and national treasuries and the electorates have avoided the follies of the 1930s; they have not assumed that only preparations for war can justify income subsidies. But those people who have "learned the lesson" of the Great Depression have also done their best to ignore what the people who survived WW 2 did to get back on their feet again. They hoarded.

The rise of grain prices that had Britain remain on food rationing longer than West Germany came not from crop failures but from the producers' decision to build up inventories rather than release them.

The Marshall Plan was about bribing the American farmers to trust the government for once to pay them a log-dated premium over the market large enough to justify current sales from the inventory and a commitment to "overproduction". Without such a Marshall Plan output could remain flat while prices rose because farmers were still reminding themselves of the lesson of the past half-decade.

After restrictions of the the risks that come with a world in which commentators on current events no one can remember.

Scott Brooks adds:

Because there's no power to be gained by actually helping people get ahead. A downtrodden, hungry, oppressed man will reach out to grant power over his life to anyone who tells him the lies he wants to hear.

Stefan Jovanovich adds:

I thought Shane was pointing out that the non-profitistas were not buying low after complaining about the speculators selling high in the past. That seemed to me a shrewd observation not only for its comment on the nature of the helping professions but also for its implicit reference to how international food relief got started in the first place. In any case, I appreciated taking what he wrote as an invitation to discuss the political origins of the Marshall Plan and an amateur exploration of how grain producers might be shifting to hoarding. (Jeff has been silent because he is busy actually trading; I suspect he is also being kind enough to refrain from publicly reminding me that current production is controlled by entirely different government rules than those around in 1948.)

Where, in this meander, does Scott's comment fit? Are we supposed to say "Oh, dear, the poor are being stupid - again?" In my own direct experience of being poor (not just broke but also cut off from the safety nets of family and professional connections), I don't remember having any "power". If I had, I would have been happy to trade it for lies, if there had also been some cash to go with it. The poor don't mind being used as the excuse for the ministering to their needs; why should they? They may get only one piece out of eight from the money being spent but it is still better than nothing.

Neo-socialism does not exist in America because "the poor" demanded it but because the markets are as cruel to the well-educated as they are to the rest of us. The Congregationalist claque in Massachusetts and the Quaker gang in Pennsylvania learned that straight off; and they did not like it. Their solution was no different from the 19th century Progressives, Kennedy's Peace Corps or the current LDS - tithes and non-profit jobs for respectable children and their elders and, of course, price supports paid for by government paper money.

The lie that will always sell is the notion that people can be helped "to get ahead" through anything but commerce.



Timed flexionic commentary can be shown in retrospect to be beneficial to the buyers of assets during price advances. This is arguably mostly evident in fixed income and currencies.

I wonder if such commentary is used during periods of declining prices to assist flexionic cultists to extricate from long positions or increase their shorts with preplanned orders. may have words to say in future days.



 "The Strange, Secret History of Isaac Newton's Papers". It's a must read.

Richard Owen writes: 

"But then at the same time he left us 10 million words, which is one of the most extensive of any scientist, or even any one person."

You need to live until about 90 and be averaging about 400 words a day from the days you're out of short trousers. Albeit the 10m seems an exaggeration since much of it was transcripts of others stuff.

anonymous writes:

"Academics have spent much time assessing Mr Niederhoffer's papers in light of his contribution to quantitative finance. It has surprised many that he had a burning obsession with furniture, being that he constantly referred to chairs in reverential fashion. He was also fascinated by forearm strength, regularly making reference to the world's grip. Most surprising of all was a seeming chemical discovery in terms of a compound called flex-ions. Sadly the papers do not elucidate and scholars continue to debate the implications."

Victor Niederhoffer writes: 

The Newton was very good with the alchemy. And I have a few of his letters where he transcribed the alchemy. As for the Niederhoffer, he has an unquestionable shibboleth against the charting, and the trend following, which led to his premature death on many occasions.



"Can Kensho Bring Google Style Search to Stock Picking?"

Apparently the program developed by Susan and me 37 years ago, and continuously used by this firm and my many followers and employees thereafter and it's many imitators has yet another instantiation.

Shane James adds:

There have been products like this around for years. Some of the brand names are/were LIM (now a Morningstar product), ECOWIN , Ranger and one other I have seen whose name I shall not mention.

Some of the differentiating variables between them are:

1. quality of source data ( stale, as is, 'real' files). One of the above uses revised economic data to test on financial market activity that occurred before the revision!!!!!!!

2. speed.

3. security.

It makes my old bones feel better to read an article whose author implies than RenTech are quaking in their boots about this or that new machine that in the hands of 99.999 percent of people would lead to the 'discovery' of non predictive, non valid relationships between asset prices.

As for the involvement of a major Wall Street bank. Let's just say you were sitting around asking the computer what happens to Y when X happens and you uncovered the grail… Well… Do you really believe that the spyware build in to these things would not report same to the in house guy at the bank.

Energy traders are particularly fond of one of the products above, to a firm, none of them use the GUI provided but rather lease the data bases so they can better protect themselves.

I am sure the latest 26 year old who wears Converse shoes around the office and has a soft play area to de stress will have the market shaking in their boots. By the way, did the protagonist contact the SEC, CFTC, the police– whoever– about the alleged calls from the hedge fund traders???

I'm just saying is all….



 Apparently, in the mid 1920s, a washing machine and a Ford Model T both cost around $300.

The ratio of those prices has changed dramatically.

I wonder why?

Shane James writes:

A magnificent relationship to ponder.

Richard Owen adds: 

Another strange example of deflationary monetary flows is that in the 1990s, when Operation Tuxedo stopped the December flow of 120k MDMA tablets, 108kg of amphetamine and 60kg of hash into Liverpool, armed robberies of bookies and posts offices in Merseyside increased by 80% the following Jan and Feb.

Pete Earle writes:

My off the cuff answer: the political machinations surrounding auto manufacturing (labor, corporate and military acquisition, etc.) leads to a large degree of government intervention, price controls, etc., in turn producing distortions, whereas washing machines are (far) less 'corporatistically' engaged. Also, a washing machine is still, for the most part (excepting, I guess, credit cards) an outright purchase, where rarely if ever is a car purchased without some sort of long-term financing. (Although the latter may be effect, and not cause.)



Canada, from Jim Sogi

January 29, 2014 | 1 Comment

 I am just back from a ski mountaineering trip in the back country deep in the Canadian Rockies. Canada is a huge country, rich in natural resources, with only 30 million people. The people are relaxed and with a lot less anxiety and tension than Americans. They lack the expertise and manufacturing base to extract much value from the raw resources.

It is a beautiful country. Things are inexpensive, especially since the recent devaluation of the loonie to US .90. There are many new immigrants to Canada from China, India and other commonwealth countries. They have a liberal immigration policy that allows commonwealth members to work there when they are young. I sense great potential in the North.

Anatoly Veltman writes: 

Jim, isn't the potential resting squarely on natural resource prices?

The problem I always had with Canada's potential was economies of scale. This population one-tenth of the US's but spread out over huge territories still needs to be managed efficiently. I'm afraid the government's burden per capita just crowds out too much.

Peter St. Andre writes: 

Here is a visualization of population density.

Shane James writes:

There is a 4 day train trip you can take from Winnipeg to Churchill (which may still be the Northern most point you can live). You can go dog sledding there, meet the remarkable Innuit people and pretend for a short time that you are Ranulph Fiennes or Amundsen.

But it's cold. Ha!



 Many different assumptions concerning the carrying capacity of the population and the rate of growth of two competing species and their current positions lead to beautiful and predictable curves in the Lotka Volterra equations for the path they will take to equilibrium. Many of these curves are pictured in google images under Lotka Volterra. The mathematics behind them are covered in most excellent books like Mathematical Biology by J.D Murray. It is interesting to contemplate whether the moves of two markets that are similar to some of the positions of these curves might take a predictable path.

Shane James writes: 

Perhaps looking at one of the two markets as the 'prey' and one as the 'predator' is also helpful

The JPY and the Bonds come immediately to mind.



 What are the major 3 body markets that orbit around each other in our solar market system and how do their epicyclic orbits relate to each other (in the future)?

Bill Rafter writes: 

I think the most important word in the Chair's sentence is "epicyclic", specifically because it is non-linear. Stocks specifically exhibit non-linear behavior, and seeming have forever. Bonds used to behave very linearly, but now behave similarly to stocks, although contrarily so. We have yet to find the defining characteristics of currency markets, but keep trying, hoping to find useful information relating to other markets. Gold is also a tough one, making one think it is a rigged game. REITS behave like a hybrid equity-debt vehicle. We tend to think of REITS as a free market version of the variable annuity (but without the huge vig).

Shane James writes: 

Arguably, and addressing prediction, the big 3 change regularly.

Simple stuff like the listing the biggest moves in X time periods is a useful, elementary starting point for cross market prediction.

Anton Johnson writes: 

Sadly, our system is unstable with the sub-stellar central mass consisting of the collective Central Banks. Orbiting, and sometimes consumed by, the central mass are the various financial instruments periodically switching in relative predominance as they accrete/disperse assets due to the actions of the brown dwarf.



 I found this article very interesting. Yet few of the investment greats have PhDs or CFAs. QED? Albeit that PhDs are overweighted vs, their population weight.

"What a Difference a PhD Makes: More Than 3 Little Letters"


Several hundred individuals who hold a Ph.D. in economics, finance, or others fields work for institutional money management companies. The gross performance of domestic equity investment products managed by individuals with a Ph.D. (Ph.D. products) is superior to the performance of non-Ph.D. products matched by objective, size, and past performance for one-year returns, Sharpe Ratios, alphas, information ratios, and the manipulation-proof measure MPPM. Fees for Ph.D. products are lower than those for non-Ph.D. products. Investment flows to Ph.D. products substantially exceed the flows to the matched non-Ph.D. products. Ph.D.s' publications in leading economics and finance journals further enhance the performance gap.

S. James writes: 

I struggle to find anything less important than the letters after one's name when assessing investment managers.

Ralph Vince writes: 

I would certainly argue that more education is preferable to less, in any field, provided such education doesn't impede someone's ability to reason things through for themselves.

Whether it facilitates thinking this way or not is not something I (nor one who does posses those credentials) can determine from our own experience.



 A moment of Zen: What do the markets and skydiving have in common? The occasional fiery crash.

Mr. S. James writes: 

Common Traits include:

1. Success in either field requires deep respect for counting.

2. Checking equipment before the taking the plunge.

3. Absolutely no hesitation at the pre-planned moment.

4. Understanding that, regardless of planning, there do exist events beyond one's control that can finish everything.

5. The weather.

6. An understanding that, despite the people around you, it really is all up to you.



 In an attempt to slow the degradation of my offspring's minds into ipad driven oblivion I took them to the Science Museum in central London today. They had both been many times but there are still many nooks and crannies yet unobserved. Their father has a particular pull towards the space exploration section as it was his childhood dream to walk on the Moon (a dream he pursued all the way to applying to be aircrew (fighter pilot status) in the R.A.A.F. two decades ago).

Anyway, there is currently a show being put on in one of the auditoriums called 'The Energy Show'. The show basically goes through many different forms of energy (Kinetic, nuclear, etc etc) in a child friendly way. The use of Van Der Graaf generators and exploding balloons of H2O2 always wins over the youngsters. A delightful use of Albert Einstein as a guide was also very interesting. If any specs are passing through London in coming weeks with young ones (7 - 100 years old) then I highly recommend it. (And while you are there….sneak off the the section on space travel).



 After putting up a chart of the Dimson, Marsh and Staunton very thorough enumeration of buying every stock in the US, from 1899 to date showing that $1 grew rather steadily to 25507  (the 1929 and 2008 declines look like blips), my college roommate Jim Wynne, in the audience, who recently won the equivalent of the Nobel prize in engineering for inventing laser surgery asked, "how could you say buy and hold" which was sung beautifully by Tamra Paselk (to the tune of "Night and Day"), is great when stocks like Kodak and Xerox have fallen on such hard times or gone bust and so few of the Dow stocks of 1899 are here today.

the chart

the table

 I explained that the complete enumeration of the triumphal trio covers all bad and all good (they even take account of the total zero of Russian stocks in 1914 and China in 1944), and there are many bad and many good that make up the totality. But on the spot, I couldn't think of a physical example to show that taking one instance of an experiment, an anecdotal approach, the flash of one outlying proton in a collider, did not determine the average results, and that diversification of 12 stocks would give a correlation of 95% or so with the results of the trio.

What physical analogy should I have used to educate my erudite former roommate who is now working on a cure for skin cancer with the same lasers he used to create laser surgery.

Shane James writes: 

What about the growth a Sequoia Tree. More generally the Allometry involved. The tree grows out & up even though some branches fall by the wayside and die.

Pitt T. Maner adds: 

I would imagine that there are some biological curves under certain restrained conditions that could be overlain for effect and be quite memorable.

Bacterial growth curve

Or groundwater testing where pumps are turned on and off over intervals and cause drawdowns that quickly rebound once the pumps are turned off.

Victor Niederhoffer adds: 

As to the reason that it goes up 30,000 a century, I attribute it to the power of compounding along with the required rate of return on investments, and the amount that the entrepreneurs must pay the investor to obtain risk capital, with the spillover effect to publicly traded issues. Amazing a 9 % compounding leads to 200 times as much as a 5% compounding (from memory) after 100 years. That's why Asian stocks are so much better values than ours. 

Steve Ellison adds: 

An event that is vivid, such as the failure of a once-giant company, may not be at all representative. Consider airplane crashes, for example, which cause many to fear flying. At one moment in 2011, for example, over 5000 airplanes were airborne over the US. How many of them crashed? Probably none.

Similarly, 20 times as many people are killed by falling coconuts as by sharks. I'm still waiting for the movie Return of the Killer Coconuts.

Gary Rogan writes: 

The simplest, albeit imperfect, analogy seems to be the number of species on earth. It is estimated that over 98% of all known species are extinct and it's likely that well over 99% of all species that ever existed are extinct.

In addition to the constant relatively steady elimination of species there are mass extinctions:

"In the past 540 million years there have been five major events when over 50% of animal species died."

And yet, will all of that biodiversity has increased over time:

"Based on analyses of fossils, scientists estimate that marine biodiversity today is about twice the average level that existed over the past 600 million years, and that biodiversity among terrestrial organisms is about twice the average since life adapted to land about 440 million years ago. Fossil records also indicate that on average species exist for about 5 to 10 million years, which corresponds to an extinction rate of 0.1 to 1 species per million."


Resources & Links