The exchange traded fund PowerShares FTSE RAFI US 1000 (NYSEArca: PRF) is described as delivering active returns with a passive discipline. The secret to this fund’s approach is in the indexing methodology.

PRF has a five-year annualized return of 6.8% compared with 5% for the S&P 500, according to Morningstar. However, the ETF does have a slightly higher standard deviation over that time at 22.6 compared with 18.9 for the S&P 500, according to the firm’s data.

The fund’s tracking index was designed by Research Affiliates. The firm’s chairman and founder is Robert Arnott. RAFI stands for Research Affiliates Fundamental Index.

Fundamental indexing is an approach that avoids weighting companies by market cap like most traditional stock benchmarks, Arnott explained at the 2013 ETF Virtual Summit.

Market-cap-weighted indices mirror the market but their “Achilles’ heel” is that the most money is allocated to the most-loved companies with the highest stock price, or the stocks with the greatest growth expectations and loftiest valuations, he asserted.

“Why not index companies based on how good their business is?” Arnott said.

He said fundamental indexing weights companies by their economic footprint and creates a value tilt relative to the market. Also, the indices are constantly re-weighted, which takes advantage of premiums and discounts in the market to economic footprint.

Fundamental indexing “turns volatility into incremental return,” Arnott explained. Boosting returns by a couple percentage points annually with the approach can make a “big difference” over 20 years, he said.

“Unlike most index funds, PRF weights its holdings based on fundamental measures of size, including book value, cash flow, sales, and dividends, rather than market capitalization. Proponents of fundamental indexing argue that these metrics better capture a firm’s economic footprint than does market capitalization, which can diverge from fundamental value,” Alex Bryan wrote for Morningstar.