Following is an interesting chart to spot bubbles within the stock market. Any time a sector’s weighting goes above 20%, it could signal trouble ahead. There were three instances since 1974 when the sector weightings for Energy, Technology and Financials exceeded that threshold and cause a bubble.
![Sector Composition of the S&P 500 by Equity Capitalization, 1974-2014](https://5kca74.a2cdn1.secureserver.net/wp-content/uploads/2014/04/Sector-Composition-of-the-SP-500-by-Equity-Capitalization-1974-2014-300x225.jpg)