If you own shares of five mutual funds (a modest number for a middle-aged person with some retirement savings), you may have stock in 300 separate companies, ea

If you own shares of five mutual funds (a modest number for a middle-aged person with some retirement savings), you may have stock in 300 separate companies, each of which may have partly-owned subsidiaries. Somehow, all this can be handled with transaction costs of about 1-2% per year.