I don't understand how we can expect a basket of all publicly traded securities (something like the ticker VTWAX) to grow above the rate of global money supply growth over the long term.

Let's assume there is a fixed amount of money in the economy, and the money supply is not increasing. For the market cap of VTWAX to continue increasing, it seems like the money must be drawn away from other areas of the economy. Assuming something like 7% share price growth per year (roughly the historical average), eventually we will reach a point where the market cap of VTWAX is 100% of all money in circulation. Heck, eventually the share price goes to infinity and is greater than all money in circulation.

I hear a lot of people recommending buying global index funds, arguing that economic growth will continue into the future. However, if the money supply is fixed, it seems like we'd probably have technological improvement without corresponding increase in share price of the global index fund. E.g., all goods and food might become much cheaper and more efficient to make but the market cap of all publicly traded companies would hover around a fixed portion of the global economy.

One possible way that I can see share prices continuing to rise is increasing money velocity, but this seems to have limits as well.

It seems like the meteoric stock price increases we've seen over the last 100 years have been due largely to increasing consolidation by large, publicly traded multinational companies alongside with actual increases to the money supply, most of which has hung around in asset prices.

I'd love for someone to help me understand why I'm wrong and why passive investing in a global index fund is a good idea even assuming no money supply increases.

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Yair Halberstadt

Jan 02, 2023


Note that the value of all index funds could easily be far far more than the sum of money in circulation. Money is only needed when the indexes are bought and sold, and so long as only a small percentage of indexes are being traded at any one time, you don't need very much money for that.

I would expect that the total value of all companies in the world is already greater than the money supply.

Also note that central banks target a fixed rate of inflation. If GDP increases, total goods production increases, and so they have to increase the money supply by more to maintain the same rate of inflation. Thus this idea of indexes increasing in value but the money supply staying fixed is not a very realistic one.

[+][comment deleted]1y10

Yes that makes sense, but is there some reason we should expect the total market cap to continue growing to huge multiples of the money supply (assuming continued technological improvement but fixed money supply)?

2Yair Halberstadt1y
Added an extra section to discuss that. The idea of increasing GDP but fixed money supply just isn't realistic, at least so long as central banks target a fixed rate of inflation.
Yeah, I'm being very hypothetical when discussing constant money supply. For the purposes of this discussion, just assume that somehow bankers decided to not increase the money supply. Are you in agreement then that over the long term, the total world index fund must approximate the total growth in money supply (I guess assuming constant money velocity)? If not can you help me understand why not? Also related: can GDP increase somehow if money supply is fixed and money velocity is fixed?
7Yair Halberstadt1y
Yes in this hypothetical, stock indexes would stay roughly constant in nominal terms, but would rise just as fast in real terms. And GDP will increase in real terms if money supply is fixed, but not in nominal terms. Both of these are because we'd have deflation.
Thanks for helping clear this up! That makes a lot of sense.


Jan 03, 2023


You’re thinking of money as being more central than it is.  Instead, try shifting your view back to barter days, where currency is just another thing that can be traded for.  So, if you had some corn to sell, you could sell it for $3, or you could sell it for 5 cans of beans.  Another way to phrase that is: You could use your corn to buy 5 cans of beans, or you could use your corn to buy $3.

Now, imagine that the stock market, instead of being valued in currency, was valued in the amount of whatever random good you want.   E.g. the s&p 500 is worth 90 trillion cans of beans, or 2 billion jacuzzis or 1.6 million 747s.    Clearly there’s nothing that limits the S&P from growing to be larger than the number of beans there are in the world, just like nothing prevents the S&P from growing larger than the amount of money in the world.

(Clearly the amount of money in the world can affect how companies can grow, since monetary policy affects lots of things.  But, while this is clearly different in magnitude, it’s no different in principle than “the number of 747s in the world affects how airlines can grow”.)