As President Xi Jinping vows to restart China’s economy, a marked slowdown in reported new coronavirus cases is helping his cause. On Monday, Chinese health authorities reported only 11 new cases outside of Hubei, the central province where the virus originated. Over the past two weeks, the number of new confirmed cases has dropped by more than 80 percent.

China’s count has been swung by changes to how individuals are officially diagnosed, leaving experts concerned over their ability to draw conclusions from the figures. “We don’t know whether the case numbers tell us about the real trend in incidents or are just a result of testing practices,” said Benjamin Cowling, head of epidemiology at Hong Kong University. In the space of a week in mid-February, China’s government switched to a broader measure of diagnosis and then rolled it back again. Many foreign epidemiologists, as well as doctors in China, argued that the broader approach was necessary, as the virus overwhelmed local capacity to conduct diagnostic laboratory tests.

So China’s National Health Commission instructed Hubei to start reporting “clinically diagnosed cases” – those diagnosed with viral pneumonia through a CT lung scan. The new category was an addition to “confirmed cases”, whereby evidence of the virus was found with a nucleic acid lab test kit, and “suspected cases”.