| 1930s | 1940s | 1950s | 1960s | 1970s | 1980s | 1990s | ||
| 1 | business and careers | 2.5% | 3.1% | 1.9% | 0.4% | 5.5% | 0.8% | 0.0% |
| 2 | leisure activities | 14.8% | 8.0% | 7.3% | 6.4% | 9.7% | 5.0% | 3.9% |
| 3 | movies/entertainers | 21.0% | 20.3% | 32.4% | 21.3% | 20.0% | 34.2% | 16.3% |
| 4 | politics/government | 10.5% | 9.4% | 14.9% | 20.1% | 19.4% | 15.0% | 7.8% |
| 5 | religion | 1.9% | 1.9% | 3.3% | 2.3% | 1.8% | 1.7% | 11.6% |
| 6 | sports/athletics | 6.8% | 5.0% | 3.7% | 4.7% | 8.5% | 1.7% | 2.3% |
| 7 | science/technology | 5.6% | 1.5% | 7.9% | 13.9% | 9.1% | 21.7% | 30.2% |
| 8 | war/military | 13.0% | 24.9% | 4.4% | 11.1% | 4.8% | 1.7% | 5.4% |
| 9 | education | 3.1% | 2.5% | 1.7% | 1.0% | 1.8% | 0.0% | 1.6% |
| 10 | fashion trends | 8.6% | 13.8% | 10.0% | 2.0% | 4.8% | 2.5% | 0.0% |
| 11 | history | 1.9% | 2.1% | 2.9% | 5.9% | 5.5% | 7.5% | 14.7% |
| 12 | crime/law enforcement | 0.0% | 0.0% | 0.6% | 2.5% | 4.8% | 4.2% | 3.1% |
| 13 | geography/places | 3.7% | 5.9% | 5.2% | 3.9% | 1.2% | 0.8% | 1.6% |
| 14 | civil rights | 0.0% | 0.0% | 0.2% | 2.7% | 0.6% | 0.0% | 0.0% |
| 15 | other | 6.6% | 1.6% | 3.6% | 1.8% | 2.5% | 3.2% | 1.5% |
| 100.0% | 100.0% | 100.0% | 100.0% | 100.0% | 100.0% | 100.0% | ||
| 1930s | 1940s | 1950s | 1960s | 1970s | 1980s | 1990s | ||
| "Light" themes | 54.9% | 53.1% | 58.7% | 38.3% | 44.2% | 44.2% | 24.0% | |
| "Serious" themes | 38.3% | 45.4% | 37.8% | 60.0% | 53.3% | 52.5% | 74.4% | |
| "Other" themes | 6.8% | 1.5% | 3.5% | 1.8% | 2.5% | 3.3% | 1.6% | |
| 100.0% | 100.0% | 100.0% | 100.1% | 100.0% | 100.0% | 100.0% | ||
| "Light" = 2, 3, 6, 10, and 14 | ||||||||
| "Serious" = 1, 4, 5, 7, 8, 9, 11, 12, and 14 | ||||||||
| "Other" = 15 | ||||||||