As the graph shows, we have been on a steady downward trend for the number of sales since the peak of 2013. (This trend is consistent with full year results as well.)
San Francisco follows a very predictable month-to-month sales cycle during the calendar year. Monthly sales are lowest between Thanksgiving and February after which the spring market kicks in reaching a peak in May or June. That's followed by a drop off through September. There's another peak in October.
This year the spring market seems to be petering out early with essentially flat sales in March, April and May.
The graph is busy but it demonstrates the consistent monthly sales cycle (good years and bad years). However, this year (in dark blue) is well below sales last year (in red) and below almost every year we've been tracking these statistics.