For a tribute edition, I am updating the book Fearfully and Wonderfully Made, which I coauthored with the late Dr. Paul Brand in 1980. During that process, I reviewed a passage spelling out the huge gap between developed countries and the developing world. I had recently seen an anonymous e-mail message floating around the Internet indicating that little has changed since 1980. It reported that 80 percent of the world's people still live in substandard housing, 70 percent are unable to read, and 50 percent suffer from malnutrition.

My curiosity piqued, I spent several days tracking down statistics from authoritative sources, only to find that the e-mail is downright wrong. In fact, the world has made major strides in the last few decades.

According to best estimates, 25 percent—not 80—of the world's population live in substandard housing. Thirty years ago the global literacy rate was 53 percent; now only 20 percent of adults cannot read. The percentage of people suffering from malnutrition has dropped by more than half, to 20 percent. Three of four people used to have no access to clean water; now three of four people have it.

Perhaps the most significant change has occurred in population growth. In 1968 Paul R. Ehrlich predicted in The Population Bomb that huge famines would occur in the 1970s and 1980s, with hundreds of millions of people starving to death. They simply did not happen.

Population experts once forecast that world population would hit a high of 20 billion, causing an intolerable strain on Earth's resources. That prediction was lowered to 15 billion, then 11 billion, then 9 billion. Some experts predict that the number will peak around 2050, and maybe even decline.

The birth rate has fallen so dramatically that ...