Refusals are a particularly important part of that growth.
So do concerns about possible large biases and, indeed, the credibility of RDD itself, since the nonresponse rate is often taken as a quality measure. Refusals may be ignorable or nonignorable. Sorting out how muchof each exists is a major challenge. This talk explores questions like the above, including a description of one way to measure the fraction of nonresponse dueto refusals that is ignorable. It is hoped that this talk, and the subsequent interaction and discussion, will move us to an enhanced set of questions and then on to better models and improved ways of estimating them.