Disaggregate productivity comparisons: sectoral convergence in OECD countries

International comparisons of productivity have used exchange rates or purchasing power parity (PPP) to make output comparable across countries. While aggregate PPP holds well in the long run, sectoral deviations are persistent. It raises the need for a currency conversion factor at the same level of aggregation as the output that is compared. Mapping prices from household expenditure surveys into the industrial classification of sectors and adjusting for taxes and international trade, I obtain an expenditure-based sector-specific PPP. Using detailed price data for up to 8 years between 1970 and 1999, I test whether the sectoral PPPs adequately capture differential changes in relative prices between countries. They work well for agriculture and the majority of industrial sectors, but not for most service sectors and for manufacturing sectors that produce differentiated products. Using the most appropriate conversion factor for each industry, productivity convergence is found to be taking place in all but a few industries for a group of 14 OECD countries. The latter results are robust to the base year used for the currency conversion.