Passage: The fifth and latest editions of the currency of the People's Republic of China have been produced since 1 October 1999. Notes have been produced in 8 denominations: old types of 1 fen, 2 fen and 5 fen, as well as new issues depicting Mao Zedong: 5 yuan, 10 yuan, 20 yuan, 50 yuan and 100 yuan. In 2004, a 1 yuan note depicting Mao Zedong first came into production. Since 1999, coins have been produced in denominations of 1 fen, 2 fen, 5 fen, 1 jiao, 5 jiao and 1 yuan.

Question: Since what year have the coins been produced?
1999