Failure to account for land quality, for example, may lead researchers to misattribute the associated differences in production to differences in the use of other inputs (Fulginiti and Perrin, 1997). Note: Sectoral production measured by value added. Given the strong concentration of the LDC labour force in agriculture, this wider productivity gap is the major cause of income divergence between LDCs and these other country groups. Labour productivity growth in ODCs has doubled to more than 3 per cent annually since the 1990s.