The poor open their pocketbooks to the churches much wider than their wealthy brethren, according to a new study of how Americans give to their churches.

The study by researcher Steven Hart also points out a striking relationship between religious denominations and the amounts of money their members give."The richest fifth of the population gives half as much, percentage-wise, as people in the lower fifth of the population. In effect, it works like a regressive tax system," said Hart, author of "Religious Giving: Patterns and Variations."

"That poses problems in terms of justice," he said. "It may be unfair the way (some) churches get income because they get it from those least able to pay rather than from those who can most afford it," Hart said.

"The people at the bottom (of the socio-economic ladder) are giving all they can afford."

The poorest fifth of church members gave, on the average, 3.4 percent of their income, while the wealthiest gave 1.6 percent. The average amount of money given by the poorest members was about $200 per year while the wealthiest gave a little more than $1,000.

Hart, who has a doctorate degree in sociology, used information collected by the National Opinion Research Center at the University of Chicago for his study. Hart analyzed that information and prepared a paper to present at the upcoming annual meeting of the Society for the Scientific Study of Religion. The study only looked at Christian denominations.

"The two most striking patterns are the giving by income levels and by religious denomination," Hart said.

"The average amount given varies enormously among denominations. The Mormons are at the top of the list. They give an average of 7.1 percent of their income to the church. The Unitarianians-Universalists and Christian Scientists are at the bottom of the list. Their members give less than 1 percent of their incomes."