"We find that expansion in voucher policy is, unsurprisingly, associated with increases in voucher revenues for parishes with schools," the study stated. "We also find that voucher expansion prevents parish closures and mergers."

At the same time, the authors seemed surprised to discover that vouchers do not subsidize religious activity beyond the operation of religious schools. Rather, the opposite occurred. "Vouchers cause a significant decrease in spending on non-school religious purposes such as religious staff salaries, mission support, and church maintenance. We also find that voucher programs lead to a significant decrease in church donations," the study continued.

Whether this is a good or bad thing depends on whether one believes that religious institutions should focus on religion or on making money by supplanting public schools. "The meteoric growth of vouchers could provide financial stability for congregations while at the same time diminishing their religious activities."

"Our numbers suggest that, within our sample alone, the Milwaukee voucher program has led over time to a decline in non-educational church revenue of $60 million. These large effects are driven by the large size of the voucher program itself," the authors wrote.