The development is perhaps better visible in a logarithmic diagram:
Apart from debunking the myth that "business-as-usual" will help the poor, it also puts into question who is benefiting from the increased global competition in agriculture commodities.
Agriculture value added per worker is a measure of agricultural productivity. Value added in agriculture measures the output of the agricultural sector (ISIC divisions 1-5) less the value of intermediate inputs. Agriculture comprises value added from forestry, hunting, and fishing as well as cultivation of crops and livestock production. Data are in constant 2000 U.S. dollars.
Looking at yield per hectare the picture is not as straight-forward. But then again, yield per hectare has never been a strong indicator of development, even if some agronomists are obsessed by it.
Check here how it looks at Gapminder