Is the world getting better or worse? Both, it seems. In January 2018, Time ran a cover story called “The Optimists,” in which the issue’s guest editor, Bill Gates, reported that things are on the whole improving. Within the month, The Bulletin of Atomic Scientists moved the hands of its Doomsday Clock thirty seconds closer to midnight, signifying that the end is as nigh as it has ever been.

The Doomsday Clock was created in the late 1940s to warn of nuclear Armageddon and now monitors other risks as well. Climate change has been factored in since 2007, bioterrorism and artificial intelligence were included in 2015, and further causes for concern will no doubt be added in due course. The clock’s hands have been moved twenty-three times since 1947, mostly in an ominous direction, but it is only a gimmick. There is no pretense that it measures anything except the degree of foreboding felt by a panel of scientists and academics.

Time’s optimists, by contrast, claim to base their sunnier outlook on precise quantification. It is “backed by data,” wrote Gates. He mentioned, among other things, a halving since 1990 of the number of children who die before their fifth birthday; a decline in the proportion of the world’s population that lives in extreme poverty, from over one third in 1990 to about one tenth now; and a rise during the past century in the number of countries in which it is legal to be gay, from twenty to more than a hundred.

There may also have been a rise in the number of books that count the ways in which things are going well. At least fifteen have appeared in English since the publication in 2000 of It’s Getting Better All the Time: 100 Greatest Trends of the Last 100 Years by Julian Simon, an economist who died in 1998, and Stephen Moore. Nobody has yet unveiled a Paradise Clock to mark the world’s measurable progress toward utopia, but many of these authors do seem to hear such a thing ticking.

Others are less sanguine, since there is no evident method of weighing good news of one sort against bad news of another. Simon’s book had a dissenting preface by his widow, Rita Simon, who was uncomfortable with the positive terms in which her husband had described the twentieth century. Despite his 146 tabulations of encouraging developments, ranging from a rise in life expectancy to increased numbers of teeth in adult mouths and of orchestras in US cities, she pointed out that the past century also saw the rise of Nazism, Stalinism, and Maoism, and the deaths of at least 170 million people at the…