George W. Bush promised tax cuts and education reform, and within the first year of his administration had delivered on both. Barack Obama promised to focus on the economy, health care and the environment. Once in office, he pushed first a massive stimulus package and then the Affordable Care Act through Congress, and he has worked with China and others in the international community on climate change, despite strong legislative opposition. As for the promises that get abandoned, many have more to do with changing circumstances than a lack of principles. (Think of Bush, an ardent free-marketeer, signing the Troubled Asset Relief Program bill during the first tremors of the Great Recession.)

In recent years, the fact-checking website PolitiFact has been paying close attention to this question, and its numbers are largely in line with what scholars find. Examining more than 500 promises President Obama made during his two presidential campaigns, PolitiFact finds that he has fully kept or reached some compromise on 70 percent of them. Similarly, Republican leaders made, by PolitiFact’s count, 53 promises before taking over Congress in 2010; 68 percent of these have been partially or fully kept.

This pattern isn’t unique to America. Scholars in Canada and Europe have examined the phenomenon and found their politicians to be, if anything, even more trustworthy. (The gap probably reflects added incentive — and increased opportunity — politicians have to carry out their policies in a parliamentary system where one party controls both the legislative and executive branches of government.) Across both time and borders, then, the data in this case is fairly clear.