There has been no increase in the average incumbent vote percentage since the 1940s. While this evidence is interesting, it has one significant limitation. It is essentially a static analysis – analyzing all incumbents at one point in time – and represents the average vote percentage for any given year. It does not capture the changes experienced by incumbents during their careers. Some incumbents are in their fourth year in office, and others may be in their twentieth.

The yearly average could be very misleading about what happens to incumbents over the course of their careers. A stable average vote percentage for incumbents from year to year may conceal considerable change in career progressions. Over time, incumbents could begin with lower initial percentages but increase their vote percentages at faster rates. The cycle of retirements and new entrants could somehow combine to produce a stable average over time, while the ability of incumbents to increase their vote percentages during their careers is increasing.

To track the dynamics of incumbent electoral fortunes, this chapter examines career changes for House members. The focus is on their ability to increase their vote percentages with successive years in office and the net increase in their vote percentages from the beginning to the end of their careers.

THE POPULATION OF INCUMBENTS

Before analyzing these two indicators of incumbent fortunes, it is helpful to review just how many incumbents there have been since 1900 in the House and how they have left.