Broadway box office had an unmistakable case of the early-fall doldrums in week 17 (Sept. 17-23), with tallies at most individual shows dropping, and the overall total falling well behind the cume logged over the same week in 2011.The year-to-year dip was attributable in part to Broadway Week, the annual fortnight of two-for-one ticket offers that helps keep attendance high during the historically slow weeks of early September. Broadway Week ended Sept. 16, but was still in effect during the sesh last year. The week’s overall total added up to $17.1 million for the 22 shows on the boards, vs. $18.5 million for the same number of titles during the same frame in 2011. Attendance of 183,074 pales in comparison with the 206,595 posted last year at this time. (Compared with the prior sesh, the week’s cume was down some $330,000.) Among the handful of shows to report week-to-week bumps in sales, “Porgy and Bess” (up almost $100,000 to $891,566) can trace its growth to last-minute biz ahead of its Sept. 23 closing. In the top 10, “The Book of Mormon” ($1,626,122) continued its reign on top, again besting “The Lion King” ($1,555,752) and “Wicked” ($1,495,735). Among the hardest hit shows last week were “Peter and the Starcatcher,” knocked down 21% to $294,536; and “Bring It On,” sliding 16% to $371,851. The 17 musicals grossed $15,415,457 for 90.3% of the Broadway total, with attendance of 155,719 and an average paid admission of $99.00. The five plays grossed $1,656,784 for 9.7% of the Broadway total, with attendance of 27,355 and an average paid admission of $60.57.