Japan
The Japanese agricultural sector accounts for about 1.4% of the total country's GDP. Only 12% of Japan's land is suitable for cultivation. Due to this lack of arable land, a system of terraces is used to farm in small areas. This results in one of the world's highest levels of crop yields per unit area, with an overall agricultural self-sufficiency rate of about 50% on fewer than cultivated.
Birth rate
As of 2016, Japan has the third lowest crude birth rate (i.e. not allowing for the population's age distribution) in the world, with only Saint Pierre and Miquelon and Monaco having lower crude birth rates. Japan has an unbalanced population with many elderly but few young people, and this is projected to be more extreme in the future, unless there are major changes. An increasing number of Japanese people are staying unmarried: between 1980 and 2010, the percentage of the population who had never married increased from 22% to almost 30%, even as the population continued to age, and by 2035 one in four people will not marry during their childbearing years. The Japanese sociologist Masahiro Yamada coined the term "parasite singles" for unmarried adults in their late 20s and 30s who continue to live with their parents.