WASHINGTON, Jan. 3 (RNS) -- Americans are giving slightly more for the day-to-day operations of their churches, but giving to missions beyond the local church has hit a 31-year low, according to a new report.

The annual report on church giving between 1968 and 1988 was released by empty tomb, inc., an Illinois firm that has tracked church giving and membership in Protestant and Catholic churches since 1972.

The report found that giving to churches lags far behind the rate of growth in personal income, especially for "benevolence" funds that go to missions beyond the local church, including global projects and denominational support.

According to empty tomb, after-tax U.S. income rose 91 percent over the two decades, but giving to congregational finances rose just 66 percent, and benevolence giving rose just 15 percent, a 31-year-low.

While overall giving was up, giving as a percentage of personal income fell dramatically. Churches affiliated with the National Association of Evangelicals saw giving as a percentage of income drop from 6.15 percent to 4 percent, a 35 percent drop. Mainline churches affiliated with the National Council of Churches saw the same rate drop from 3.31 percent to 2.96 percent, a drop of 10 percent.

Sylvia Ronsvalle, who co-authored the study with her husband John, said the most troubling trend is that of the increased money given by parishioners, more is being earmarked for day-to-day operating expenses and not for mission and care-giving projects. For every dollar of increased giving, 94 cents went for operating expenses that benefit just the congregation, while only 6 cents went to benevolence funds, such as feeding programs and disaster relief.

"Our giving patterns really are an indicator of our spiritual condition, and what the number suggests is that our temperature is cooling toward our religion," Ronsvalle said.

Ronsvalle estimated that if church members gave the biblical standard of 10 percent of their incomes back to the church, donations would surge by an additional $131 billion. The responsibility falls on church leaders to push for big projects, such as hunger relief, that would create the incentive to give, she said.

"If people are not being challenged to do something great, they lose interest," she said. "They put the church on the same par as any other consumer purchase and they will not sacrifice for something that isn't capturing their imaginations."