Improving Survey Response Rates with Visible Money

In mail surveys and in advance letters for surveys in other modes, it is common to include a prepaid incentive of a small amount such as $5. However, when letters are addressed generically (such as to “Resident”), advance letters may be thrown away without being opened, so the enclosed cash is wasted and the invitation or advance letter is ineffective. This research note describes results of an experiment using a nationally representative sample of 4,725 residential addresses to test a new way of letting mail recipients know their letter contains cash and is therefore worth opening: an envelope with a window revealing $5, so the cash is clearly visible from outside the sealed envelope. We also tested the USPS for evidence of theft, and we compared First Class and Priority Mail postage. We found no evidence of theft. We found no difference in response rates between Priority Mail and First Class, making First Class much more cost-effective, and we found that visible money increased the response rate to a mail survey from 42.6 to 46.9 percent, at no significant cost.