Next, we estimate the proportion of sales that occur in states where the seller lacks nexus (and therefore is assumed not to collect sales taxes). Third, we distribute these sales across states, and multiply by the appropriate tax rates. In this section, we describe the data, methodology and assumptions we used in conducting each step. Where appropriate, we note where our approach differs from that adopted in the Fox Study and explain why we believe our approach is more appropriate for evaluating alternative sales tax policies.