The primary sector tends to make up a larger portion of the economy in developing countries than it does in developed countries. For example, in 2018, agriculture, forestry, and fishing comprised more than 15% of GDP in sub-Saharan Africa but less than 1% of GDP in North America.
In developed countries primary sector has become more technologically advanced - witness for instance the mechanization of farming as opposed to hand-picking and -planting. More developed economies may invest additional capital in primary means of production. As an example, in the United States' corn belt, combine harvesters pick the corn, and sprayers spray large amounts of insecticides, herbicides and fungicides, producing a higher yield than is possible using less capital-intensive techniques. These technological advances and investment allow the primary sector to employ a smaller workforce - in this way, developed countries tend to have a smaller percentage of their workforce involved in primary activities, instead having a higher percentage involved in the secondary and tertiary sectors.
Developed countries are allowed to maintain and develop their primary industries even further due to the excess wealth. For instance, European Union agricultural subsidies provide buffers against fluctuating inflation-rates and prices of agricultural produce. This allows developed countries to export their agricultural products at extraordinarily low prices. This makes them extremely competitive against those of poor or underdeveloped countries that maintain free-market policies and low or non-existent tariffs to counter cheap goods. Such price differences also come about due to more efficient production in developed economies, given farm machinery, better information available to farmers, and (often) larger scale.
Some economies exhibit a particular emphasis on the basic food-providing parts of the primary sector (farming and fishing), wishing to guarantee via autarky in food-production that citizens can eat even in extreme circumstances (such as war, blockade, or sanctions). The agricultural revolution may not have preceded the industrial revolution entirely by chance.