The size of triangle B, the net increase in national income due to migrant workers, can be estimated in percentage terms as: 1/2 (3 per cent decrease in wages x 11 per cent immigrant worker share of the labour force x 70 per cent share of labour in national income, or 1/2 x (0.03 x 0.11x 0.7 =0.002) = 0.001, meaning that national income in the United States was increased by 1/10 of 1 per cent because of the presence of migrant workers