Comparing Tax Rates Using OECD and GTAP6 Data

In prior research, Babiker, Metcalf, and Reilly (2003) computed capital and labor tax rates to augment GTAP 4 data that did not comprehensively cover taxes. Recently, we updated these tax rates to 2001 to match the GTAP 6 base year. We realize there was an attempt to improve representation of taxes in GTAP 6, but as admitted by GTAP this was as yet incomplete. For those who might require a more complete tax accounting we have followed an approach that has the benefit of, at least in the aggregate, reconciliation with widely available tax receipt data. This note compares the tax rates derived for the OECD countries using this approach to those provided by the method GTAP uses. Those who are interested in economic impacts of fiscal measures--such as assuring revenue neutrality by raising tax rates in the face of a policy that reduces economic activity--may want to consider amending the tax data in GTAP. Alternatively, it may be useful to discuss the differences we note to as part of on-going efforts to improve data reported in GTAP. Table 1 provides tax rates based on our methodology as well as from GTAP 6, aggregated to be approximately comparable. More disaggregated GTAP 6 tax rates are provided in Tables 2-3. GTAP6 reports taxes on factor income (rTF) as well as income taxes (rTO) whereas BMR combine income and factor taxes into a composite factor tax. We construct an accumulated factor tax (ACC) from the GTAP6 tax data which we believe is directly comparable to the BMR tax rates by the formula: ACC = 1 - (1 - rTO)(1 - rTF)