I'm trying to figure out the correct P/E ratio for the S&P500 based on the last twelve months of earnings. The S&P website quotes 22.49 as of 5/31/08:
S&P | Indices > Equity Indices - S&P 500 - Month End Data
But given the declines in the market this year, that seems a little high. By comparison, Yahoo reports the P/E on the S&P500 ETF (SPY) at the same point in time to be 14.22. I imagine the ETF is going to be off a little due to expenses and dividends, but that is a sizeable discrepancy.
Meanwhile, Vanguard reports a P/E of 17.6 for its S&P500 index fund (VFINX) at the end of May:
Any thoughts on which number is correct?