My friends who make their living doing survey methodology have taught me that the answer to almost every survey methodology question is: "It depends." Having just read how a prenote and $5.00 incentive didn’t do much for the response rate on UM’s Survey of Consumer Attitudes (SCA) I have come across an article in the Summer 2005 edition of POQ that shows an advance letter on a phone study creating about a 5% bump in response rate and an advance postcard about a 3% bump. The authors also conclude that the cost of the prenote efforts were less than the cost of the additional dialing.
The obvious question: why does it work here and not for the SCA? Well, that’s not easy to answer. On its face, this study (done at MSU) seems to have been as rigorous at the SCA (for example, up to 15 call attempts). But the response rate on the MSU study was only around 25%, roughly half of what the SCA gets.
One hypothesis might be that the UM folks are better at this sort of study than the Sparties. The UM folks get people with a phone call where the Sparties need an advance communication of some sort. But that’s just a guess.
All that said, my takeaway on this is that a prenote is worth considering if you’re concerned about response rate. I’d certainly recommend some tests of our own. But don’t ask me to guarantee that it will work because my answer will be, "It depends."