Between 6% and 12.5% of skilled nursing providers are believed to inflate their self-reported staffing and quality measures, causing inaccuracies in their overall ratings, according to a report published Thursday.

Researchers from the Brookings Institution and the University of Connecticut School of Business identified a trend of facilities’ self-reported staffing and quality measures shifting to higher star ratings between 2009 and 2013. During that same time period, the distribution of on-site inspection ratings between the star levels remained unchanged.

That trend could mean one of two things, the research team wrote in the report on the first-of-its-kind study.

“On one hand, supporters can argue that increased levels of self-reported measures are genuine and represent an honest effort by nursing homes to constantly improve their services,” the team said. “On the other hand, however, skeptics may argue that the improved ratings are not legitimate but are rather a result of nursing homes’ success in developing strategies to manipulate the system and inflate their ratings.”

To figure out which of the two scenarios was behind the rating shift, the report’s authors analyzed ratings and nursing home complaints, and conducted a prediction model to estimate the “extensiveness” of facilities’ rating inflation.  

The prediction models showed that between 6% and 12.5% of facilities likely inflate their self-reported ratings. The team’s findings also identified a “significant positive association” between financial incentives and improving star ratings, which may motivate inflating behaviors.

“Although CMS has implemented minor improvements to its rating system, it is still largely based on self-reported measures and does not address the issue of inflation,” the researchers wrote. “[Our] results can be used to strategically focus future audits on the nursing homes which are most likely to be inflators, and help CMS improve the rating system.”

Click here to read the full report, “Five-star ratings for sub-par service: Evidence of inflation in nursing home ratings.”