The study of 30 charities shows that 48 per cent of people who signed up in the first eight months of 2010 had stopped donating within 11 months, and it is predicted that figures for the full year will show that percentage to be nearer to the 2008 high of 56 per cent.
It also shows that the proportion of sign-ups who fail to make a first payment reached a record 30 per cent in 2011. These no-shows are not included in the attrition figures.
The sign-up figures for 2011/12, published earlier on the same day last week, have been hailed as the most successful ever, showing that the association's 140 members recruited 863,407 donors. This includes 238,273 by street (as opposed to doorstep) fundraisers. The overall figure, from which no-shows are not deducted, is 40 per cent up on 2010/11.
Meanwhile, the PFRA's mystery shopping results, also released last week, reveal the quality of street fundraising is dropping. Although the score for 2012 remains high at 90 per cent, it is down from 94 per cent in 2009, which the association admits is a concern.
Cathy Pharoah, professor of charitable giving at the Cass Business School, says: "I think these figures are showing a classic trend when people go all out for volume growth at risk of quality.
"The PFRA notes that more fundraisers have been taken on, working at sites that can accommodate fewer fundraisers, which means they might be working harder and getting more successful at squeezing the juice out of the public. But you then see higher attrition rates because some of the donors recruited were basically more reluctant to make a commitment and didn't know how to say no.
"Does a high sign-up level lead ultimately to more committed donors, regardless of the cost in terms of attrition? There's probably quite a high cost, in terms of public image, in increasing the volume and frequency of street solicitation."
Xanthe Swift, agency regular giving manager at the British Red Cross, agrees there is a need to focus on quality. She says the BRC has improved its own mystery shopping and training over the past two years, focusing on "the conversation on the street".
The charity researched why people fail to keep up their donations. "People cannot say no, they feel guilty, but later on they cancel for financial reasons," she says.
There have been occasions, she says, when fundraisers have boosted sign-up numbers by saying to donors that they can "cancel it right away".
Swift says another factor in attrition is saturation. "Street fundraising was brand-new and innovative," she says. "Over the past two to three years we have certainly seen negative media coverage. There has been a change in public perception as well."
Ian MacQuillin, head of communications at the PFRA, says the spike in no-shows is something to keep an eye on. "On the whole, there is nothing in the figures that should cause undue alarm," he says. "Every year for the past decade, someone has looked at the recruitment figures or the attrition rates and predicted the imminent demise of face-to-face fundraising.
"However, the proof of the pudding is that, for the charities that use it, F2F is the most cost-effective and predictable method of donor recruitment."