In the 1970 world census of agriculture, seven countries asked farmers how they transported their crops to the first point of sale (to a market, or a trader, etc.). All seven countries were reasonably poor (under US$1000 per capita GDP) but it is striking how common transporting crops to market by foot was in the two African countries compared to the South/Central American countries and Jordan (still a low-income country at the time the census of agriculture took place, though it grew spectacularly in the 1970s due largely to remittances). Of course, there are physical differences between the countries — Zaïre was and is about two-thirds of the size of Western Europe. But it does show some of the difficulties faced by agriculture, and particularly export agriculture, in Africa in the twentieth century.
Share of farmers who took their produce to the first point of sale by foot:
Gabon – 80%
Zaïre/Democratic Republic of Congo – 71%
El Salvador – 10%
Panama – 20%
Suriname = 3%
Jordan – 30%