Small-cap stock funds ran neck and neck with midcap funds for much of the past 10 years, but stumbled a bit more in last year’s September-October market correction. They’ve since regained their momentum. What would a $10,000 investment made on June 30, 2005, buy you in 10 years? If made in the average small-cap mutual fund, you’d get $24,230 by July 1 this year, according to Morningstar Inc.