Theft has an article with the following headline and subheading:
Fentanyl-related deaths are declining. What’s behind the decline?
The evidence points to changes in drug supply
It’s an excellent article, but there’s actually no evidence to support the subheading (which is usually written by the editor, not the journalist).
The article does provide evidence that there has been a recent decline in the amount of drugs seized, but that could reflect lower supply or lower demand. To avoid ‘reasoning from a change in quantity’, you need to look at simultaneous changes in both price and quantity. Does rising fentanyl prices deter users, or does reduced demand for fentanyl lead to lower prices?
Another article suggests that at least in Minnesota it could be the latter:
In recent months, the price to buy fentanyl on the street in the Twin Cities metro has dropped to $1-$2 per pill, a veteran narcotics investigator with the Hennepin County Sheriff’s Office confirmed.
That’s down from a few years ago, when the price was about $20, said Hennepin County Sheriff’s Maj. Rick Palaia, adding that the cost still extends far beyond the metro. . . .
“Whether supply falls or not, the number of deaths will certainly fall,” Palaia concluded. “And we will continue to educate, and we will continue to try to get as much fentanyl off the streets as possible.”
The FT article suggests what seems to me the most plausible explanation for the recent decline in fentanyl deaths, which started on the East Coast:
A third possibility is the idea of Nabarun Dasgupta and colleagues at the US academic collective Opioid Data Lab that fentanyl, like an infectious disease epidemic, has now worked its way through its susceptible population. Some died, others figured out ways to use the drug without overdosing, shrinking the remaining population of fentanyl-naïve drug users. The wave-like dynamics at work here means that theoretically it would also fit the east-west pattern.