An annual study by the Fraser Institute has again called into question how generous Canadians are compared with Americans — though some Canadians say they keep their generosity off the books.

The institute's 2015 generosity index, based on 2013 tax data, said tax claims provide the most reliable evidence of individual giving. Its information shows Americans are more likely to give money to registered charities and more of it.

The Fraser Institute has been tallying the index since at least 1999, always showing U.S. generosity outstripping Canadian.

The institute's results, released Thursday, contradict some of the information released by Statistics Canada in early 2015 in a survey on volunteering and charitable giving.

According to the Fraser Institute, in 2013, about 22 per cent of Canadians claimed donations to registered charities on their taxes, giving on average 0.5 per cent of their income.

Charles Lammam, director of fiscal studies at the institute, compared that with U.S. tax filings.

"Americans are much more generous than Canadians," he said. "So much so that in some cases, they are 2½ times more generous when we look at the share of income being donated."

The Fraser Institute says Americans are more generous than Canadians based on income tax filings. (CBC)

In the U.S., the average donor gives 1.39 per cent of their income. When the Fraser Institute calculates the average donation, the amount works out to more than $5,000, compared with $1,500 in Canada. The institute acknowledges that figure is inflated by wealthier donors.

"That difference translates into $13 billion more that Canadian private charities would have received had Canadians donated at the same rate of income as their American counterparts," Lammam said.

He also noted that there had been a downward trend over the past decade.

"All provinces have seen a drop in both the share of tax filers donating to charity, as well as the share of income being donated," he said. "These trends are concerning, because it now raises new challenges for the private charities in Canada to secure the resources they need to provide the valuable services to the most vulnerable in our society."

Statistics Canada differs

Statistics Canada's survey said the proportion of Canadians who made a donation in 2013 was down from 2010, but the amount donated was up.

"Between 2010 and 2013, the total amount donated by Canadians to charitable or non-profit organizations increased by 14 per cent to $12.8 billion," the Statistics Canada report said.

Meanwhile some individual Canadians say they don't keep tabs on what they give.

Victor Sawa says he donates hundreds of dollars that don't make it into his tax filings. (CBC)

Victor Sawa made a donation to the Salvation Army kettle fund at a Regina mall. He said he doesn't always ask for a receipt.

"I mean, what the heck, it's Christmas," he said. "I'm not here for the tax receipt."

Sawa said his tax claims don't reveal hundred of dollars he gives to charities every year.

Major Kristiana MacKenzie of the Salvation Army.

Maj. Kristiana MacKenzie of the Salvation Army believes Canadians are generous.

"Christmas time in particular, we have such a giving spirit that most people aren't thinking of that tax receipt," she said. "They just want to help."

The Fraser Institute study doesn't count increasingly popular crowdfunding campaigns such as GoFundMe.