That is an interesting question. I guess one way to approximate a very rough, back-of-the-envelope type of answer would be to look at the average daily dollar volume traded and the total market capitalization. So for instance with the Nasdaq we have approx. $30 trillion in market cap and approx. $400 billion of average daily volume, a factor of 75. So in the best-case situation where each share trades exactly once, it would take approx. 75 trading days for the market to turn over once. However, let's take a more pessimistic assumption (though probably still not pessimistic enough) that shares are selected randomly to trade. We can use the classic ball-and-bins type of probability to estimate how many days it would take until let's say 95% of dollar value had turned over at least once, which produces an estimate of roughly 225 trading days, so let's round it up to 1 trading year (these are very rough estimates). So then assuming that roughly 95% of the Nasdaq market cap has turned over in the past year, then the average market cap over the past year is not a bad ball-park estimate of the cost basis. (I invite any real mathematicians out there to tell me where I went wrong.)
My fear in such calculations is that we leave the big whales that do not move, outside. For example the CEO of Nvidia has 4% Nvidia that in today's value is 160B, but the basis is from the IPO, so more like $40M. So now our back-of-the envelope calculation is 160B off.
People with large holdings are required to file with the SEC and you can search those records online going back to the mid 1980s.
Someone could download a dump of the whole thing (the SEC has a link and updates it every night) and assemble all of the various documents in a way to get a decent estimate.
An example Form 4 (which will show cost basis of acquisitions):
In my humble opinion,It would be 0 as there is no transaction taking place. The original question is about stock buyers not stock holders which is often related but not always.
I dont think your pessimistic scenario is nearly slow enough. There is a large buy and hold component of the market, with high frequency trading on the margin.
The random sale model doesn't account for pensions, mutual funds, and individuals that hold. Where would firms like Berkshire Hathaway fit into this model?
I imagine the distribution of stock hold duration is nonlinear/logarithmic
I don't consider they serious, because they could buy penny stocks, which are unregulated and are very frequent target for fraud.
> pensions, mutual funds
Funds are better than individuals, because usually they have some strategy and hiring professionals to control things, but they also prone for mistakes.
Berkshire Hathaway is very special type of investor, as from Buffet cite, they only invest as major owner, avoid to be minor. Because as major they have much more access to internal kitchen of company, not just standard for IPO open balance with omitted details.
