How many shares trade across US markets in a day?

Question

You are handed no data, but you know the total US stock market is worth very roughly $50$ trillion dollars, and that a fraction of a percent of it changes hands on a normal day. Solve in your head.

Estimate how many shares trade across all US equity markets in one day. Aim: under 60 seconds.

Accepted Answer

First estimate the dollar volume, then divide by a typical share price. - Assume about 0.5–1\% of the market's value turns over daily. Take \sim 0.7\% of \50T: 0.007 	imes 50 	imes 10^{12} \approx \3.5 	imes 10^{11} \;(\350	ext{ billion}). - A typical share might trade near \150. Divide: \frac{3.5 	imes 10^{11}}{150} \approx 2.3 	imes 10^{9}. So on the order of a few billion shares per day (roughly 2–5 billion given the loose inputs). Takeaway. When a count is awkward to reach directly, route through dollars: value 	imes turnover gives dollar volume, and dollar volume divided by unit p…

How many shares trade across US markets in a day?

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