Top 10 US companies now hold 36.9% of market cap, near 1932 record
iblanco_finance · x · 2026-09-28
Using CRSP monthly data from WRDS (all US common stocks since 1926, share classes grouped by company), the author finds the ten largest US companies hold 36.9% of total market value — approached only in May 1932 (36.7%). The share hit 38.1% in mid-May, fell to 33.8% by late June as megacaps dropped 11%, then recovered. Long-run average is 23%; the low was 12% in Sept 1993. Listed companies fell from a peak of 7,428 (July 1997) to 3,645 by end-2025. Caveat: 1932 data cover only NYSE.
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