Using different reference totals can potentially have an important impact on the income shares. In their analysis of a number of alternatives for computing reference totals, some based on different National Accounts aggregates, some being fixed shares of GDP, and others departing from tax assessments adding estimated incomes of nonfilers, Roine and Waldenstr€om (2010, Appendix C) show that there are indeed single years or episodes when differences are notable. Overall, however, the main trends in the results are robust to which alternative is chosen.