Why is measured productivity so low in agriculture?

In poor countries, labor productivity in agriculture is considerably lower than in the rest of the economy. We assess whether this well-known fact implies that labor is mis-allocated between the two sectors. We make several observations that suggest otherwise. First, the same fact holds for US states where severe mis-allocation is implausible. Second, the gaps between the marginal value products of agriculture and non-agriculture are considerably smaller when measured through wages than through labor productivities. Third, labor productivity in agriculture is severely mis-measured in the US.