One of the largest value ETFs is the the Vanguard Value ETF (NYSEArca: VTV). VTV follows the tracks the CRSP US Large Cap Value Index and is one of the most widely followed value ETFs. CRSP includes sales/price and historical earnings/price ratio as well as 12-month forward earnings/price ratio and dividend yield to form its value indexes.

Value investing is a popular long-term investment strategy. Value stocks have historically outperformed growth stocks, or companies with high earnings expectations, in almost every market over the long-haul. For instance, the MSCI USA Value Index has outperformed the MSCI USA Growth Index by an annualized 81 basis points since 1974 through September 2015.

The energy and financial services sectors, frequently the two largest sector allocations in many value ETFs, have been laggards this year, explaining the slack performance of the value factor on a broader level.

“What’s been left behind in this market has largely been energy and financials. Energy and financials make up almost 40 percent of the value index, and we think the risk reward around those two sectors look quite attractive,” Zirin said, according to CNBC.

Value stocks usually trade at lower prices relative to fundamental measures of value, like earnings and the book value of assets. On the other hand, growth-oriented stocks tend to run at higher valuations.

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