[HN Gopher] Ask HN: What is the actual cost basis of the stock m...
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       Ask HN: What is the actual cost basis of the stock market?
        
       Does anyone know what is the actual cost basis for the entire US
       stock market.  I mean at what price did the current stock holders
       got/bought their stocks.
        
       Author : whatever1
       Score  : 10 points
       Date   : 2025-03-10 19:52 UTC (3 hours ago)
        
       | s1artibartfast wrote:
       | I dont think anyone has that data. Individual companies dont have
       | a record of who owns their stock and what they bought it at. Even
       | individual owners sometimes dont know their own cost basis, let
       | alone their broker or some centralized authority. This is further
       | complicated by the fact that >50% of trades now occur outside of
       | exchanges [1]
       | 
       | You might be able to estimate a similar attribute by looking at
       | IPO history and additional primary offerings, but that also has
       | major challenges. It doesn't include pre-IPO owners that retain
       | stake, buybacks, ect. What is Zuckerberg's cost basis in Meta?
       | 
       | Interesting question though....
       | 
       | https://www.bloomberg.com/news/articles/2025-01-24/wall-stre...
        
         | whatever1 wrote:
         | I don't even directionally have an idea how much is it. Is it
         | like 80% of the current total market value or 8%? My back of
         | the envelope math plus very coarse assumptions lead me closer
         | to 80%.
        
           | s1artibartfast wrote:
           | To be clear, you are talking about the aggregate for the
           | current holders, understanding that actual cost basis will be
           | different for every person with stock? Some people will have
           | long invest duration with tiny cost basis, some will have
           | cost basis over 100%.
           | 
           | My ballpark guess is less than 80%. Most of the stock market
           | is owned by households, either directly through equities, or
           | indirectly through mutual funds and pensions [2, p14]
           | 
           | Most individuals and pensions are long term positions, with
           | buying and selling to increase or decrease a position, not
           | buying or liquidating entire portfolios.
           | 
           | If I guess the average hold time is ~5 years, that would be a
           | about a 60% basis.
           | 
           | US total stock market cap in feb 25' was 67 Trillion, Total
           | market cap in feb 20' was 40 trillion. [1]
           | 
           | What conclusion are you trying to draw from it? From an
           | individual perspective, I care more about my cost basis in my
           | market account, than the cost basis for an individual stock.
           | I might have a 95% cost basis my current holding, but a 5%
           | cost basis for my entire account(what I put in the market)
           | 
           | https://focus.world-
           | exchanges.org/issue/february-2020/market...
           | https://www.sifma.org/wp-content/uploads/2019/10/SIFMA-
           | Insig...
        
             | gizajob wrote:
             | I'd hazard that average hold time is much shorter. What
             | makes you say 5 years? My gut tells me that the majority of
             | stocks are held by whales moving them in and out on a
             | constant basis nowadays.
        
             | whatever1 wrote:
             | I am trying to understand how much the stock market can
             | drop before we destroy realized value (cash). Or how much
             | money is not used in the economy, but rather it is tied to
             | the stock market.
        
       | o_nate wrote:
       | 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.)
        
         | whatever1 wrote:
         | 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.
        
         | s1artibartfast wrote:
         | 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
        
       | blackeyeblitzar wrote:
       | One way to look at this is to look at the valuation of each
       | company at the time of IPO, and see where it is now. Stock
       | changed hands but you could think of growth relative to when the
       | public could trade that stock. It's not perfect - just an idea.
        
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       (page generated 2025-03-10 23:02 UTC)