Founded in 1860, Standard & Poor's is an American financial company known for its stock market indices, credit ratings and market analyses. Standard & Poor's (S&P) indices are major benchmarks in the world of finance. The S&P 500 index is the best known of the S&P indices. It represents 500 of the largest companies listed on US stock exchanges. This index is generally considered to be the best indicator of the performance of US large caps. The S&P 100 is a subset of the S&P 500, comprising 100 of the largest companies in the S&P 500. But beyond the S&P 500 and S&P 100, Standard & Poor's manages a wide range of indices, covering various sectors and market segments. For example, the S&P MidCap 400 and the S&P SmallCap 600 target mid-cap and small-cap companies respectively. The S&P indices are calculated on a free float-adjusted market capitalisation basis, which means that only publicly available shares are included in the index calculation (providing a more accurate representation of market value). The S&P indices are widely used by investors to track the performance of the US market, for portfolio management and as a basis for comparing the performance of investment funds. The composition of the S&P indices is regularly revised to reflect changes in the stock market. Inclusion criteria include company size, liquidity and sector representation.