When it comes to stocks so far this year, bigger has proven to be better.
Large-cap stocks, as measured by the S&P 500, have outperformed the small-cap index by around 8 percent in 2014. According to Matarin Capital's Nili Gilbert, that trend is likely to continue for the rest of the year.
On CNBC's "Fast Money" on Wednesday, Gilbert laid out three reasons why large-cap stocks will continue to outperform.
Gilbert cited valuation as the first indicator of big-cap dominance. "At this point small stocks are looking pretty expensive relative to large."
Momentum was Gilbert's second indicator of large-cap dominance. As Gilbert noted, small-cap stocks outperformed large-caps from 2008 to 2013, with the Russell 2000 gaining 52 percent in that period vs. a 26 percent return for the S&P 500.
Gilbert said that "the longer-term multi-year cycle with small having done so well for so long looks to reverse."
Lastly, Gilbert said rising interest rates could ultimately hurt small-caps.
"It becomes a concern that smaller companies not only tend to be more leveraged than larger companies on average, but also tend to borrow at higher rates," she said.
Both names have already seen big gains year-to-date, and if Gilbert's large-cap outperformance thesis holds true, there could still be more gains ahead.
—By CNBC's Michael Newberg