From what I’ve seen in California, this is due to the presence of Uber. Via the WaPo:
New federal statistics show that the rate of drunken driving in the United States fell to a 13-year low in 2014, the latest year for which data is available. The rate of driving under the influence of illicit drugs has not changed meaningfully in recent years but remains slightly lower than it was in 2008 and 2009 at the start of the Obama administration.
In 2014, as part of the National Survey on Drug Use and Health, 11.1 percent of Americans 16 or older told federal interviewers they had driven under the influence of alcohol in the past year. There’s a certain amount of squishiness about these numbers, given that they’re self-reported. Respondents may have different thresholds for what they think constitutes “impairment” or they may be reluctant to report what is essentially illegal behavior in an interview.
But the survey has been administered with the same methodology since 2002, meaning it provides a particularly useful measure of drunk and drugged driving trends over time. And the findings are fairly unequivocal: In 2002, 15.3 percent of Americans said they drove drunk, 5 percent said they drove under the influence of one or more illicit drugs, and 3.3 percent said they drove under the influence of both simultaneously. By 2014, those numbers had fallen to 11.1 percent, 4.1 percent and 2.4 percent, respectively.
