Historical P/E ratios of small-cap vs. large-cap stocks?

According to the Wall Street Journal Website, average trailing 12-month P/E ratios on the major large-cap indices are currently (late September, 2011) around 12-14, which is slightly cheap compared to the very long-term historical record and very cheap compared to recent history.

However, the Russell 2000’s average P/E is about 40. There seems to be tons of data on the typical historical P/E ratios for large cap indices, but not so much on small cap indices like the Russell 2000.

Is this huge difference in P/E between the large cap indices and the Russell 2000 historically typical – since small-caps are generally faster-growing companies – or is it unusual?