The research also indicated that, despite massive donations to the tsunami and other disaster appeals this year, the number of donors giving to humanitarian charities has dropped by 8 per cent since 2000.
The figures showed an average drop in the number of givers of nearly 10 per cent across all sectors - although environmental charities are attracting nearly a third more donors than they did five years ago.
Experian's Data Insight Team analysed more than 80,000 responses to charity questionnaires distributed to members of the public during 2000 and 2005.
The survey showed that 50 per cent more women than men donated in 2005, and that women aged 18 to 30 are the most active in giving to charity.
Richard Hill, charity consultant for Experian's marketing services division, suggested that two factors might have contributed to the overall drop in donor numbers.
One was that, in the past few years, companies had begun to place their corporate social responsibilities further up the business agenda, providing employees with opportunities to fundraise in large groups instead of donating alone.
Hill said: "People can now give to charities en masse with their colleagues through their employer's chosen fundraising activities. Why set up a standing order when you can do your bit through your employer?"
He said that the second reason could be to do with "donor fatigue" - particularly when it came to donations to humanitarian causes.
The research was contradicted by the RSPCA, which said that it had not experienced this "apparent trend" and that the numbers of direct debit givers, for example, had continued to rise.
Mark Astarita, director of fundraising at the British Red Cross, disputed the findings and the notion of donor fatigue. He said 2005 had seen a 100 per cent increase in donations to the Red Cross compared with 2004, with the organisation breaking the £100m barrier for the first time ever in one year.
He added that he would be "incredibly surprised" if Charities Aid Foundation annual figures did not show an increase in giving to international charities.