Back in happy 2013, in a letter to Berkshire Hathaway (BRK.A) (BRK.B) shareholders, Warren Buffett suggested that most investors put their long term money into low-cost S&P 500 index funds. He even noted that his will stipulated that 90% of the money he inherited from the family should be invested in such a fund. It’s worth noting the well-known fact, that in the long run it’s hard to beat broad indices, and many portfolio managers burned while aspiring at those kind of ambitious goals.

Berkshire Hathaway's portfolio includes two S&P 500 exchange-traded funds (ETFs): the SPDR S&P 500 ETF Trust (SPY) and the Vanguard 500 Index Fund ETF (VOO). Second, Buffett mentioned in his 2013 letter to Berkshire shareholders that he "recommends Vanguard Group."

Based on these two pieces of evidence, there's good chance that Buffett's chosen S&P 500 index fund is exactly VOO – even for mere reason that its expense ratio is a very low figure at 0.03%, compared with SPY's 0.0945%. With VOO, we can see, to no surprise, Technology is the leading sector in its structure with an exposure rate of nearly 30%, followed by Health Care, Financials, Consumer Cyclical, and Communication Services. Over the past 10 years, the S&P 500's average total return, including reinvested dividends, has been nearly 12.5%. However, this period was featured by an unusual bull run. Over the past 50 years, the S&P 500's average annual total return has been nearly 10.7%. It’s still beating core inflation by a wide margin, but it would hardly make an investor his (her) fortune.