TOKYO - The total of extra working hours at manufacturers in September, a key gauge of the state of the economy, fell 14.7% from a year before to 12.1 hours, extending the decline for a seventh consecutive month, the Ministry of Health, Labor and Welfare said Wednesday. The corresponding figure for all industries dropped 8.1% to 9.0 hours, the seventh straight year-on-year drop, the ministry said in a survey of all businesses with a workforce of five persons or more.