In addition to the national estimates presented in the text, we also estimated potential un-collected revenues on a state-by-state basis. As explained in the text, our survey of firms’ tax collection practices in each state allowed us, for the firms surveyed, to directly estimate uncollected taxes on a firm-by-firm basis. (Indeed, our national estimates for these firms
represent the summation of uncollected taxes across states and firms.) For firms not surveyed, i.e., un-surveyed firms from the Internet Retailer 500 and firms in the “tail,” we estimated potential uncollected revenues though a two-step process.