From a resource standpoint, the important point of this comparison is that including the marginal external costs of production and allocating resources based on the full social cost results in a higher price for the good (Ps > Pp) and less output (Os < Op) than only including the private costs.
Today, the nation's farmers are 17 years older than the average American worker, with the ranks of farmers who are 75 years and up outnumbering those in their prime working years of 35 to 44. One big reason U.S. farmers are going gray: spiraling costs.
That depends on the region of the world that you refer to. In most industrialized countries is now 80 and increasing. The regions with more longevity are country areas in semi-industrialized countries with moderate climate where the average life span of men is 90 and of woman 95. In countries where cardiovascular disease and environmental pollution are factors of public health concern, the average is 70 for men and 75 for women.