The concept of the yen was a component of the Meiji government's modernization program of Japan's economy, which postulated the pursuit of a uniform currency throughout the country, modelled after the European decimal currency system.Before the Meiji Restoration, Japan's feudal fiefs all issued their own money, hansatsu, in an array of incompatible denominations. The New Currency Act of 1871 did away with these and established the yen, which was defined as 1.5 g (0.048 troy ounces) of gold, or 24.26 g (0.780 troy ounces) of silver, as the new decimal currency. The former han (fiefs) became prefectures and their mints private chartered banks, which initially retained the right to print money. To bring an end to this situation, the Bank of Japan was founded in 1882 and given a monopoly on controlling the money supply.
Following World War II the yen lost much of its prewar value. To stabilize the Japanese economy the exchange rate of the yen was fixed at ¥360 per $1 as part of the Bretton Woods system. When that system was abandoned in 1971, the yen became undervalued and was allowed to float. The yen had appreciated to a peak of ¥271 per $1 in 1973, then underwent periods of depreciation and appreciation due to the 1973 oil crisis, arriving at a value of ¥227 per $1 by 1980.
Since 1973, the Japanese government has maintained a policy of currency intervention, and the yen is therefore under a "dirty float" regime. The Japanese government focuses on a competitive export market, and tries to ensure a low yen value through a trade surplus. The Plaza Accord of 1985 temporarily changed this situation from its average of ¥239 per US$1 in 1985 to ¥128 in 1988 and led to a peak value of ¥80 against the U.S. dollar in 1995, effectively increasing the value of Japan’s GDP to almost that of the United States. Since that time, however, the yen has greatly decreased in value. The Bank of Japan maintains a policy of zero to near-zero interest rates and the Japanese government has previously had a strict anti-inflation policy.
The spelling and pronunciation "yen" is standard in English because when Japan was first encountered by Europeans around the 16th century, Japanese /e/ (え) and /we/ (ゑ) both had been pronounced [je] and Portuguese missionaries had spelled them "ye".[b] By the middle of the 18th century, /e/ and /we/ came to be pronounced [e] as in modern Japanese, although some regions retain the [je] pronunciation. Walter Henry Medhurst, who had neither been to Japan nor met any Japanese, having consulted mainly a Japanese-Dutch dictionary, spelled some "e"s as "ye" in his An English and Japanese, and Japanese and English Vocabulary (1830). In the early Meiji era, James Curtis Hepburn, following Medhurst, spelled all "e"s as "ye" in his A Japanese and English dictionary (1867); in Japanese, e and i are slightly palatalized, somewhat as in Russian. That was the first full-scale Japanese-English/English-Japanese dictionary, which had a strong influence on Westerners in Japan and probably prompted the spelling "yen". Hepburn revised most "ye"s to "e" in the 3rd edition (1886) to mirror the contemporary pronunciation, except "yen". This was probably already fixed and has remained so ever since.