Having slipped 2.2 percent in September from an all-time high in August, the National Association of Realtors Pending Home Sales Index, a seasonally adjusted index for which 100 denotes “an average level” of activity, ticked down another 1.1 percent in October to 128.9 but remains 20.2 percent above its mark at the same time last year with 19.8 percent less on less inventory on the market, which is pushing prices up, versus 134 percent more inventory on the market in San Francisco, year-over-year, and the highest share of reductions since late 2011.