As pointed out by Warren Buffett, the percentage of total market cap (TMC) relative to the U.S. GNP is "probably the best single measure of where valuations stand at any given moment." In all the three approaches discussed above, the fluctuations of profit margin are eliminated by using GDP, the average of trailing 10-year inflation-adjusted earnings, and peak-P/E, revenue, or book value etc. This confirmed again the conclusions of earlier studies: The aggregated activities of insiders can serve a good indicator for locating the market bottoms.