This book shies away from evaluating current levels of any given issue, and instead focuses on change over time. Is a particular issue getting worse, better, or staying about the same? Advantageously, this approach is reasonably objective, and all parties on a given issue should be able to agree on how it is changing (assuming suitable data). For example, fewer Americans smoke today than in 1965, when 42% smoked; this is true whether you're a tobacco company executive or an anti-smoking activist.

Nonetheless, even trends over time are also subject to subjective evaluation. Just because something is getting better doesn't necessarily mean that it's getting better fast enough to suit people. We can see substantial progress and still want much more. As former president Bill Clinton once said, "The crime rate is down, the welfare rolls are down, the food stamp rolls are down, the teen pregnancy rate is down . . . And yet, we all know that all those things that are going down are still too high." Such ethical judgments are part of living in society, but I don't emphasize them. Instead, I focus on describing how things are changing, and others can debate whether these changes are enough.

The main focus of this book is tracking changes over time, but with some issues I also describe differences between groups-especially when people's experiences with an issue vary widely. With the United States, I highlight differences based on gender, race and ethnicity, class, age, and other social fault lines. With the world, I compare countries or regions to underscore international differences.

Going into this book I didn't have strong preconceptions about whether the world is getting better or worse; I treated this book as a chance to learn about it myself. My goal here is accuracy, and I tried to go wherever the data took me. Ultimately, I conclude that many things in the world are indeed getting better, but I did not set out to write a "positive" book. Indeed, this book catalogues issues that are getting better as well as some that are getting worse. Writer Robert Samuelson underscores the importance of this approach when he writes:

We'd be better off with a more balanced view of our present condition. We need a clearer understanding of our strengths and shortcomings, because we are ill served by either excessive optimism or excessive pessimism. The first regularly leads us into romantic schemes that are doomed to fail, while the second may condemn us to hopelessness and continued paralysis.

The meat of this book is statistical description. Surveys, census data, and other sources provide rich and accurate descriptions of the population as a whole. However, sometimes we lose the power of individual actions and local situations when we rely solely on statistical data. To counter this, and to provide a richer understanding of changes in the world, I also include stories that highlight unique, altruistic contributions made by people trying to improve the world. One of the conclusions of this book is that the world is improving so much because so many people are working to make it a better place. To help us appreciate the impact of this altruism, I tell some of their stories.