During the first few years of the twenty-first century, Americans have already contended with a remarkable amount of political and economic tumult, ranging from the Sept. 11 attacks to the collapse of the 1990s economic boom to military conflicts in Afghanistan and Iraq. Uneasiness and caution have ruled the financial decision-making of many American households. Now, recently released statistics from the Barna Research Group indicate that this pervasive apprehension may have contributed to a dramatic one-year decrease in the number of American homes that tithe to their churches.

Barna's data shows that only 3 percent of adults contributed 10 percent of their 2002 income to churches, which marks a 62 percent decrease from 2001 when 8 percent of American adults tithed. Among born-again Christians, the decline was similarly steep, from 14 percent in 2001 to 6 percent in 2002. Barna attributes the sudden drop to a variety of factors, including the soft economy and ongoing terrorism threat. But he also pegs shifting church demographics—younger adults don't share their parents' and grandparents' convictions about tithing.

This generation seems not so much put off as mystified by the concept. Their questions are honest enough: "Who came up with the figure of ten percent? Why should we take this figure as authoritative? Isn't tithing legalism?" Here, as in most churchly matters, a bit of history can go a long way.

Most discussions of tithing begin with the Old Testament precedent, first recorded in Genesis 14:20. After winning an astounding victory in battle and retrieving his nephew Lot along with all his lost possessions, Abram thanked God by giving Melchizedek one-tenth of all he had. Then, in Numbers 18:21, we find tithing included ...