Open
offices
Incumbents
seeking re-election
2011
27%
73%
2012
29%
71%
2013
50%
50%
2014
33%
67%
2015
36%
64%
2016
45%
55%
2017
63%
38%
2018
39%
61%
2019
45%
55%
2020
36%
64%
Total
37%
63%