Growth investors tend to view small-cap stocks more attractively than large-cap stocks in a bull market. The reasoning is simple: when stocks are rallying, smaller companies with the potential for more rapid revenue and earnings growth typically outperform during times of economic expansion. However, the reverse is often true – namely, that small-cap stocks typically under-perform when global economic growth slows.

Small-cap stocks, as a whole, have not performed well so far in 2015. The Russell 2000 Index, a collection of 2000 small-cap stocks, is down 3.5% year-to-date through October 23. By comparison, the S&P 500 Index, which includes large-caps, was down approximately 1.5% through the same period.

Worries over slowing economic growth in the emerging markets have caused stock prices to stagnate this year, and that has naturally affected small-caps. However, there are some small-cap–focused mutual funds that have outperformed the Russell index and broader market this year.

Among the list of top-performing mutual funds, three in particular that may be interesting to investors are the Emerald Growth Fund Investor Class (FFGRX), the Oberweis Small-Cap Opportunities Fund (OBSOX) and the Wasatch Core Growth Fund (WGROX). These funds each have a modest required minimum investment of $2,500, which means they are available to most retail investors. And, all three funds maintain prolonged track records of strong returns.

Source: Yahoo Finance

The main reason these funds have performed so well despite a relatively poor climate for small-cap stocks in general is that they have opportunistically taken advantage of high-growth sectors of the economy. For example, these funds hold higher-than-average allocations to the health care and financial services sectors, which have seen rising growth over the past several years. The Emerald Growth Fund (FFGRX) allocates 22% of its assets to health care and another 15% to financial services. In fact, healthcare is the highest market sector allocation for the Oberweis Small-Cap Opportunities Fund (OBSOX), at 27%.

Investors should not solely look at total return when analyzing mutual fund performance. That is because fund expenses are an equally important component of a mutual fund’s total return. Mutual funds charge investors expenses, typically expressed as a percentage of an investment. Since expense ratios can vary among different funds, investors should consider a fund’s expenses before investing.

The three small-cap funds mentioned above have outperformed the Russell index, but the funds charge relatively high fees that directly detract from performance. But there are many solid small-cap mutual funds that do not charge such high fees. For example, one mutual fund that has performed well so far in 2015 and offers a more competitive expense ratio is the Fidelity Small Cap Growth Fund (FCPGX). This fund returned 3.4% to investors year-to-date through September 30. This fund charges a 0.9% annual expense ratio, which beats its peer category of 1.3%.

Investors looking for higher growth among mutual funds could consider small-cap mutual funds. Small-cap equities tend to outperform large-cap equities when markets are rising, due to their higher growth potential. This year, while the Russell 200 Index has not performed well, there are still small-cap–oriented funds that have generated above-average returns for investors.