Police department stats are notoriously ambiguous -- filled with variables and reporting standards that shift from year to year. They do not provide a definitive portrait of a city's crime scene, but a single component of a greater narrative. As such, a few arbitrary facts can help contextualize -- though not necessarily explain -- the numbers.
In 2006, the Board of Supervisors passed an ordinance stating that marijuana offenses would be city law enforcement's "lowest priority." That policy coincided with the beginning of a rise in reported narcotics incidents in Mid-Market -- from 251 in 2005 to 459 in 2008.
In 2008, the SFPD had 2,375 sworn officers, according to a 2009 pamphlet soliciting applications for the SFPD Police Chief job opening. By 2011, the department had fewer than 1,800. During that stretch, however, reported narcotics incidents in Mid-Market dropped by more than two-thirds, from 459 to 144. It is hard to say how much of this drop is because there was less drug dealing, how much is because there were less officers on the street to spot the drug dealing, and how much is because officers shifted their focus to other crimes.