That article is citing the same study that was discussed in the Washington Post this morning- here :
A quote from the more substantial Wapo article:
"Experts cautioned that the effects of the minimum wage may vary according to the industries dominant in the cities where they are implemented along with overall economic conditions in the country as a whole.
And critics of the research pointed out what they saw as serious shortcomings. In particular, to avoid confusing establishments that were subject to the minimum with those that were not, the authors did not include large employers with locations both inside and outside of Seattle in their calculations. Skeptics argued that omission could explain the unusual results.
"Like, whoa, what? Where did you get this?" asked Ben Zipperer, an economist at the left-leaning Economic Policy Institute (EPI) in Washington. "My view of the research is that it seems to work," he said. "The minimum wage in general seems to do exactly what its intended to do, and thats to raise wages for low-wage workers, with little negative consequence in terms of job loss."
Read more here:
https://www.washingtonpost.com/news/wonk/wp/2017/06/26/new-study-casts-doubt-on-whether-a15-minimum-wage-really-helps-workers/?utm_term=.d3374099f113