Brilliant yet practical work. Thank you for sharing your findings! Statistical portfolio diversification can be accomplished with only 13-15 individual holdings....although outside of the statistical measure of diversification, practically-speaking, there are so many vectors to diversify along (domestic vs intl, market cap size, sector, industry, etc) that even 50 holdings can't possibly fully diversify nevertheless, I'm thinking, just looking at the trends on the focus/rebalancing frequency slide, that there may be some meaningful incremental gains by trimming the monthly rebalancing amongst just 13-15 stocks....assuming of course they're not all clones of one another like just semiconductor stocks.