It's been a year since Colorado became the first US state to permit the commercial sale of marijuana for non-medicinal purposes, and statistics which hint at the impact of legalization have just started to emerge. With these come two conflicting reports— one from the pro-legalization Drug Policy Alliance (DPA), and another from the anti-legalization Smart Approaches to Marijuana (SAM). The two together make for an interesting read. Unsurprisingly, there’s been an increase in the amount of cannabis consumed in Colorado, as well as in Washington, where it has also been legalized.

Both states already had a higher than the US average use of marijuana, but between 2011/12 to 2012/13 the percentage of over-18s who had used marijuana in the past year rose from 16.1% to 18.9% in Colorado, and from 15.3% to 17.6% in Washington, compared to a national increase from 11.6% to 12.2%. Past monthly use of marijuana by 18-25 year olds in 2012/13 was 29.1% in Colorado and 25.6% in Washington, compared with a 18.9% US average.

Of course, an increase in marijuana use isn't in and of itself a bad thing; what matters are the other costs and benefits to society and individuals that legal and increased use creates. Predictably, the two reports paint very different pictures of these.

The DPA point out that Marijuana possession rates in Colorado have fallen 84% since 2010, from over 9,000 arrests a year to under 1,500. However, SAM's report claims that citations for the public display of marijuana have rocketed - from 183 in 2013 to 668 in 2014 in Denver alone.

Both violent crime and property crime fell in Denver in 2014. Violent crime was down by 2.2% in the first 11 months of 2014, compared with a 1.1% decline the year before. Burglaries were down 9.5%, and overall property crime 8.9%. This, the DPA say, is evidence of legalization’s success. However, at the same time, SAM report that drug violations in Denver are up 12%, disorderly conduct up 51%, and public drunkenness up 53%.

SAM also report that the number of citations given for driving under the influence of marijuana in Colorado have risen markedly between 2013 and 2014. However, despite concerns that marijuana legalization would result in an increase in traffic fatalities, the DPA point out that Colorado saw a 3% fall in the number of fatal accidents in 2014, continuing a 12-year downward trend.

SAM’s report contains a handful negative incidents which can be directly attributed to legalization, including a rise in the number of children in ER from the accidental consumption of marijuana edibles, and an increase in people attempting to make hash oil and setting themselves on fire. However, perhaps the most interesting claim of the report is a quote from a Colorado policeman that legalization has ‘done nothing more than enhance the opportunity for the black market’.

A potential reason for continued underground dealing is that, with taxes, legally-purchased weed is up to twice the price of that on the street. However, the market demand for legal weed has far exceeded earlier estimates, including those of the Department of Revenue’s. Unsurprisingly, there’s also been a huge increase in the amount of marijuana which has been stopped from leaving Colorado for other states — a 400% rise between 2008 and 2013, SAM claim. This has resulted in neighbouring Nebraska and Oklahoma suing Colorado for the flow of marijuana across state lines. However, whilst this might present a nice new business for criminal gangs or college students, it seems unlikely that it would increase the black market's size or power compared to pre-legalization.

Of course, it’s also very difficult to know if other reported stats like falling violent crime can actually be linked to marijuana legislation, and even things like a rise in disorderly behaviour arrests could be down to other factors. But there are a few stats we can be certain about, and these come down to cold hard cash.

Retail marijuana sales raised $40.9m in tax for Colorado between January and October 2014, and that’s not including revenue from medical sales, licenses or fees. Of the revenue collected, $2.5m has been directly set aside to fund more health professionals in Colorado public schools, many of whom will focus on mental health support and drug use education programs.

Legalization has been great for entrepreneurship, too. 16,000 people have been licensed to work in Colorado's marijuana industry so far, and unemployment is at a 6-year low. A study of two marijuana dispensaries by the University of Denver’s economics department found that they generated $30m of economic output and 280 jobs between January and July 2014 – and whilst paying ten times the amount of tax of a typical restaurant or store.

Though we can measure things like tax intake, both the DPA and SAM’s reports highlight the need for much more high-quality data, which can help unravel the effects of legalization, and quantify their impact. This is something which will likely to emerge with time, but without reliable facts and evidence campaigners on both sides will cherry-pick stats to confirm their existing views — which is no good for the policymakers elsewhere who are watching this experiment closely. (It's certainly a shame that Theresa May is not one of them....)

Nevertheless, a year on and we can tell a couple of things. Legalization is obviously a learning curve. To avoid serious backlash, marijuana users should stop lighting up where they shouldn’t (at school, in public places, before driving, etc), whilst the green industry should probably do more to provide information on the strength and dosage of new products, and particularly edibles.

However, it’s also clear that legalization is a major boon to the public coffers, takes millions of dollars of business out of the hands of criminals and into legitimate businesses, and is a major win for liberty.

SAM may be concerned about the 100 kinds of marijuana gummy bears out there, but these THC-ripened snacks are also testament to the creativity and entrepreneurship that flourishes when the state gets out of the business of deciding what peaceful activities adults are allowed to partake in, for recreation and for profit.