After a group of economists published a study claiming the Sturgis Motorcycle Rally in South Dakota last month may have triggered a “superspreading event” that led to over 250,000 new cases of Covid-19, skeptical experts broke down the numbers, and found them lacking.
The study, published by the IZA Institute of Labor Economics, claimed to have compared anonymized cell phone data from in and around the Sturgis area during the 10-day rally, which saw over 500,000 attendees, and compared that data to the rate of new Covid-19 cases in the county that hosted the rally, as well as counties that sent the most attendees, showing an increase in both over the following weeks.
But a recent report published by Jennifer Dowd, deputy director of the Leverhulme Centre for Demographic Science at the University of Oxford, says the 250,000 estimate is at best an “absolute worst-case scenario number,” and the actual number of infections may only be in the hundreds, with contact tracing efforts showing just over 250 cases in 12 states linked to the rally since Sept. 2, according to NPR.
The IZA study, which wasn’t confirmed by epidemiologists, “doesn’t provide a model of infectious disease transmission—a pretty major oversight,” Dowd writes, adding “the authors don’t outline what transmission on this scale would have to look like to reach 266,796 infections.”
Dowd argues it’s unlikely rally attendees had time to get infected, ride home, infect others, and have those new infections show up in county statistics by September 2, just two weeks after the end of the rally.
Her theory is backed up by Ashish Jha, dean of Brown University’s School of Public Health, who noted on Twitter the study’s raw data shows no infection spikes in counties where the authors say attendees came from that weren’t already underway.
17%. That’s the number of positive Covid-19 tests in South Dakota, according to the Covid Tracking Project, one of the highest-case positive percentages in the nation.
South Dakota’s Republican Gov. Kristi Koem blasted the study on Twitter, writing, “this report isn’t science. It’s fiction. Under the guise of academic research, it’s nothing short of an attack on those who exercised their personal freedom to attend Sturgis.”
The IZA study received massive media coverage. Some observers have criticized the media for reporting so heavily on the study while ignoring an earlier one by the same authors that found a Trump rally in Tulsa this June didn’t lead to a spike in coronavirus cases, while also largely dismissing the possibility that the nationwide Black Lives Matters protests could have spread the virus. South Dakota is one of the few states that never enacted a mask mandate. South Dakota has reported at least 16,437 cases and 183 deaths since the beginning of the pandemic, according to the New York Times.