The linked data shows 19 murders in the first five months of 2013, 11 murders in the same period in 2014. First, this is very noisy data to make any predictions from. (I guess it's a good thing to have so few murders that it's hard to make generalizations.) March 2014 alone had 5 murders compared to three last year. Second, this isn't a 52.9% drop, even if you exclude May, which makes the drop from 17 to 9. It's a 47…
One of the arguments against legalization is that once marijuana is legal, we would see a significant _increase_ in crime.[1] So a __statistically__ insignificant result is not a __politically__ insignificant result.
1: From TFA: ""Expect more crime, more kids using marijuana and pot for sale everywhere," said Douglas County Sheriff David Weaver in 2012."