Circulation of the SF Chronicle has slipped to below 400,000 for the first time in decades. The FAS-FAX report by the Audit Bureau of Circulations’ released this morning (May 8) showed the Chron’s circulation had fallen 15 percent to 398,246. The news was also bad in San Jose, where the Mercury News’s circulation continued its free fall, dropping 7.6 percent in the past six months to 242,865. E&P provides a look at circulation numbers from across the country. [Chron: News aggregators are taking readers away from newspapers]