Published: Oct 21, 2010 12:22 PM EDT
Updated: Oct 21, 2010 9:22 AM EDT

SEATTLE (AP) - Women across nearly every income level gave significantly more to charity than men, nearly twice as much in some cases, according to a study by the Center on Philanthropy at Indiana University.

Nonprofits have long suspected that women were the driving forces behind many of the gifts they receive, but they haven't had much proof. But the results of this study are so decisive and consistent, they can stop wondering, said Debra Mesch, director of the university's Women's Philanthropy Institute.

The study offered several factors the researchers thought contributed to the growing generosity of women: More women are working and their incomes have grown, more have college degrees that yield greater earning power, and the percentage of women who make more money than their working husbands is now about 26 percent.

The study released Thursday found women give more in every income bracket except one: Those with incomes of between $23,509 and $43,500.

The data used for the study was not broken down by gender, so researchers looked solely at households headed by single men or single women, including adults who have been divorced, widowed or never married. They looked at the donating patterns of about 8,000 American households.