There might be less marijuana in a typical joint than was previously thought, a study has found.
An average joint contains 0.32g (0.01oz) of marijuana, researchers discovered.
This is less than previous estimates, which suggested a single joint held anywhere from 0.3g to 0.75g (2.6oz) of cannabis, with some users reporting amounts as high as 1g (0.04oz).
The United States Office of National Drug Control Policy used 0.5g (0.02oz) as its baseline.
Experts said knowing how much cannabis a joint contains could help governments find out how big the market for marijuana is - and how much is being imported into their country.
The research was carried out by Dr Greg Ridgeway, an associate professor of criminology and statistics at the University of Pennsylvania, and Beau Kilmer, of the RAND Drug Policy Research Center .
Dr Ridgeway said finding our how much cannabis is in an average joint was important.
This is because it turns out to be a critical number in estimating:
* How much marijuana is being consumed [nationwide]
* How much drug-trafficking organizations are putting on the market
* And how much states might expect in revenue post-legalisation.
The pair created a mathematic model from looking at 10,000 marijuana transactions during 11 years and from more than 40 communities.
The information came from the US Justice Department's Arrestee Drug Abuse Monitoring program.
As part of the program, people in prison - not just those imprisoned on drug-related charges - were interviewed about substance use and how much drugs cost.
'The data had information on 10,628 transactions related to marijuana,' Dr Ridgeway said.
These included whether the person had bought joints or loose marijuana, where the interactions happened, and how much they had paid.
'Some will tell you about loose purchases, in grams or ounces, and give you a dollar amount,' Dr Ridgeway said.
'Other people will say "I bought four joints and paid $20 [£15],"' he said.
'If I paid $5 [£3.80] for a joint and you paid $5 for 0.5 grams, that gives me some information. If they're the same price, they must be roughly the same weight.'
However, the prices do not include any inflation that occurred during the decade the data covered.
Also, drugs prices differ across areas, depending on the market.
For example, Dr Ridgeway said marijuana is more expensive the further away a sale happens from where it was grown, due to added shipping costs. And some drug sellers offer bulk discounts. To account for these factors, the researchers had to create a drug-pricing model.
'My colleague and I used this dataset and an economic model that's been used for about 30 years now to untangle weight and price, to estimate the average joint weight,' Dr Ridgeway said.
'That all boils down to about 0.3 grams, which is much less than previously thought.'
Knowing this precise number could help the US government better understand how much marijuana is trafficked from Mexico, as well as the size of the illicit marijuana market, he added.
It also has the potential to improve discussion about legalisation of the substance, both for places considering it and for US states that have already taken that step.
The study will be published in the journal Drug and Alcohol Dependence next month.
Re: How much marijuana is there in the average joint?
Yeah, I host a card game every Friday night, and there are usually 20-30 roaches that get left in the ashtrays, and I would imagine each roach is about 1/2 gram, and they're all specific strains of killer green bud that the boys have as a favorite.
One of our players is a little older, and his wife always makes me promise there is no smoking.
Even though the apartment we play in above my garage has 15 ft. vaulted ceilings, and the room is 28' x 24', I often have to turn on an exhaust fan to supplement the open windows for our friend George, or if it's too cold to open the windows. George was born in Greece, is 89 years old, and he had one of his lungs removed when he was in his early 70's, although he continued smoking cigarettes for another 5 years. Now he's on oxygen, has cancer in his remaining lung, and is sensitive to smoke.
Still, George manages to grow a stout cannabis garden every year, like all of our players.
Those that say, don't know. Those that know, don't say.