| 1996 | 2000 | 2004 | 2008 | 2012 | 2016 |
By actual election results |
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Mean victory margin | 16.3 | 21.7 | 21.5 | 19.8 | 18.3 | 20.6 |
Percentage of competitive districts | 17.7 | 9.7 | 5.1 | 11.5 | 14.0 | 7.4 |
Percentage of safe districts | 65.3 | 78.2 | 83.0 | 72.9 | 67.4 | 75.4 |
By the district normalized presidential vote |
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Mean victory margin | 10.0 | 11.2 | 11.6 | 12.0 | 13.3 | 14.7 |
Percentage of competitive districts | 30.6 | 28.0 | 25.1 | 25.5 | 19.3 | 15.6 |
Percentage of safe districts | 39.5 | 45.3 | 48.0 | 49.9 | 57.5 | 61.8 |