For years, the estimates of nonfatal gunshot injuries published by the Centers for Disease Control and Prevention have grown increasingly unreliable — in 2017, they were more suspect than ever. But researchers have continued to cite the numbers as authoritative. Last year, a CDC spokesperson defended the data, saying the agency’s experts were “confident that the sampling and estimation methods are appropriate.”

Now the CDC is taking measures to curtail the spread of its most unreliable estimates. The 2016 and 2017 gun injury figures have been hidden on the agency’s public data portal, with a footnote stating “Injury estimate is not shown because it is unstable.” The CDC will hide unstable estimates for all injury types within the next six months, according to a spokesperson. Also, the option to include statistical information about how reliable or unreliable the estimates are is now enabled by default. Until recently, it was disabled by default.

The trouble is, the departing hospital and its replacement may treat very different numbers of injuries. From at least 2000 to 2010, a hospital labeled Primary Sampling Unit 41 submitted data to the CPSC’s panel. Raw numbers published by the CDC and CPSC show that this hospital treated a very small number of gunshot injuries: fewer than 10 each year from 2005 to 2010, and just 20 total over that six-year span. When this hospital dropped out of the database in 2010, it was replaced halfway through 2012 with a different one that treated a dramatically larger number of gun wounds: 793 during its first full year in the dataset.

The new hospital added over 22,000 nonfatal gun injuries to the 2015 national estimate — more than 100 times greater than the most ever contributed by its predecessor. This hospital — one of the 60 or so used in the sample — accounts for over one quarter of the total estimated gunshot injuries that year, which is the most recent data available.

Other gun injury estimates are less susceptible to the distortions that hospital selection can introduce. The Healthcare Cost and Utilization Project, another database under the Department of Health and Human Services, uses data from more than 950 hospitals to create its own gun injury estimate — far more than the CDC. Among multiple sources of national gun injury data that The Trace and FiveThirtyEight reviewed last year, the CDC’s was the only data set that consistently showed an increase in gunshots from year to year — an indicator that its estimates are out of step with other reliable data sources.

senorgrand wrote: Wed Aug 28, 2019 7:10 pm A big fat red flag for "research" on "gun violence"