The rise in approval ratings of former President George W. Bush has received some attention this week, in advance of the opening of his presidential library in Dallas. But that rise is exactly what one would expect, based on the history of other ex-presidents’ approval ratings.

Presidents who are unpopular in their final months in office – like Gerald R. Ford, Jimmy Carter and the first George Bush, all of whom lost presidential elections – typically become more popular out of office. All three of those former presidents had approval ratings exceeding 60 percent at various points over the past 20 years, according to separate polls by Pew and Gallup.

The approval rating of the elder Mr. Bush peaked at 74 percent in early 2000, according to Gallup. Mr. Carter hit 69 percent in 1999, before drifting down to 52 percent in 2010. Mr. Ford reached 71 percent in 1999 (when the economy was booming and Americans were evidently feeling charitable toward their ex-presidents), and he was at 61 percent in 2010. The trend starts before presidents leave office, with their approval often rising in between election day and inauguration day.

“Presidents’ retrospective approval ratings are almost always more positive than their job approval ratings while in office,” writes Jeffrey M. Jones of Gallup. “Former presidents likely transcend politics when they leave office, moving into a more nonpolitical role compared with the highly political environment in which presidents operate.”

Even Ronald Reagan and Bill Clinton, popular throughout much of their presidencies and re-elected by comfortable margins, have had higher approval ratings since leaving office than they did in office, on average.

The pattern here doesn’t apply only to former presidents, either. When prominent people leave the battles of daily politics, their approval ratings tend to rise. Hillary Rodham Clinton’s favorability rating stood at 65 percent at the end of her tenure as secretary of state, a job mostly above the partisan fray. As recently as 2008, in the midst of her primary campaign against then-Senator Barack Obama, her approval rating was only 48 percent, according to Pew. If she runs for president again in 2016, her rating will almost surely decline from 65 percent.

George W. Bush’s trajectory is most similar to that of President Lyndon B. Johnson. Mr. Bush left office with among the lowest approval ratings of any president, hobbled by an unpopular war. Mr. Johnson, worried he would lose his own Democratic Party’s nomination because of the Vietnam War, chose not to run in 1968. Mr. Johnson’s approval rating hovered around 40 percent in his last year in office, while Mr. Bush’s hovered around 30 percent.

By 2010, 49 percent of Americans approved of Mr. Johnson’s performance as president, with 36 disapproving, according to Gallup. In a recent Washington Post-ABC poll, 47 percent approved of Mr. Bush’s perspective, and 50 percent disapproved.

The one exception to the pattern is Richard M. Nixon, the only president to resign from the office. His approval rating was only 29 percent in 2010 and has not exceeded 40 percent in any poll Gallup has published.

These historical patterns, obviously, are not destiny. It is possible that George W. Bush will become more or less popular over time, depending on events like the Arab Spring and on the details that eventually emerge about his tenure. But it isn’t surprising that Mr. Bush has become more popular as a former president than he was as president. It would be news if he were not.