Evidence since 2021 broadly supports Friedberg’s prediction about speculative early‑stage listings and non‑diversified investors. First, there was a historic boom in speculative IPOs and SPACs in 2020–21, with U.S. IPOs hitting record levels and SPAC IPOs exceeding 600 in 2021; this boom abruptly reversed in 2022 as rates rose and markets sold off. (nasdaq.com) Subsequent analysis shows that a large share of SPACs launched in 2020–21 either liquidated or now trade below their typical $10 issue price, meaning many investors who bought and held individual de‑SPAC stocks suffered significant losses. (nasdaq.com) Second, retail investors did in fact concentrate heavily in a small set of ‘sure thing’ meme stocks such as GameStop and AMC during the 2021 short‑squeeze episode; after extreme spikes driven in part by r/WallStreetBets, many of these stocks later declined sharply, leaving late entrants with large losses. (en.wikipedia.org) Third, similar dynamics played out in concentrated high‑growth strategies: Cathie Wood’s ARK Innovation ETF (ARKK), which was filled with speculative, early‑stage or unprofitable tech names, peaked in February 2021 and then experienced a maximum drawdown of about 80% by late 2022; investors who piled in near the peak lost on the order of two‑thirds of their capital and badly lagged diversified benchmarks like the S&P 500 and Nasdaq‑100 over the subsequent years. (portfolioslab.com) Finally, regulators and the financial press report billions of dollars in recent losses from pump‑and‑dump and meme‑style scams in thinly traded micro‑cap listings, again typically involving investors putting outsized positions into a handful of touted stocks that later collapsed. (investopedia.com) While we lack a clean, comprehensive dataset that directly compares all single‑name bets to diversified baskets of the same speculative listings, the realized pattern—proliferation of early‑stage speculative listings, many individual blowups, heavy retail concentration in a few ‘already made’ stories, and large subsequent losses—matches Friedberg’s qualitative claim that non‑diversified investors in single hot stocks were very likely to have a “tremendous learning experience,” whereas only more diversified exposure and/or broader portfolios had a reasonable chance at acceptable long‑term returns relative to the market.