I would guess that it's not ridesharing, but app-based hailing which reduced drunk driving, by reducing the friction of hailing a ride. There is also the added effect of there being more vehicles available, which reduced wait times, but that can be achieved with increasing the number of medallions, so I don't believe there is a direct need for companies like Uber and Lyft to reduce drunk driving.

Well, "can be achieved in theory" and "has happened in reality" are vastly different things. Some potential counter-arguments:

- If it can be achieved via such a simple change, then why wasn't it?

- Medallions and gig economy have vastly different incentive models, which tie very deeply with coverage and supply volume

- What of the countless anecdotes of taxi no-shows even after rideshare became prevalent?

- In most markets, it took a multinational giant burning through billions of dollars to get competitors to start playing catch up technology-wise

- etc

It is likely a local effect, as taxi hailing apps have succeeded in countries where ridesharing has failed, such as South Korea. I don't know the exact mechanisms behind the different circumstances, but as I said before, I believe the benefit is from the app-based aspect and not the ridesharing aspect.

I'm not too informed about the South Korea market specifically either, but reading about it, what the news suggest is that the decrease in DUIs in SK are heavily correlated to progressively stricter DUI laws over the years.

I'm not sure to what extent we can infer a correlation between the app-based aspect and DUIs there.

Though to be clear, I do think the app-based aspect plays a role. It's just that when I say "rideshare", I assume we are talking about the whole package as it exists in reality, as opposed to dissecting what aspects of Uber affect what types of statistics.

The rate of drunk driving had already been decreasing for years.