In 2016, the Russell 2000 Index of small-capitalization stocks gained 21% with value-oriented, defensive stocks taking charge in a year that witnessed growing uncertainty around the Brexit vote in the U.K. leading into June and uncertainty surrounding the U.S. presidential election leading into November, according to a FTSE Russell note.

However, U.S. small-caps have made a 180 turn this year, with the Russell 2000 and the iShares Russell 2000 ETF (NYSEArca:IWM), which reflects the benchmark Russell 2000 Index, both up around 6.0% so far this year, with growth-oriented, dynamically driven companies leading the charge.

“As evidenced by their abrupt shift in performance drivers in 2017, US small cap stocks are a very sensitive asset class and closely reflect shifting economic and political environments. This is why it is important for investors to have a high quality range of index tools allow them to properly measure and plan before investing in this critical asset class,” Ron Bundy, CEO of North America Benchmarks, FTSE Russell, said in a note.

Related: Why Value ETFs Could Bounce Back

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