A few months in 2009 are described as having been:

1. Prices do occasionally fall, even in modern economies. 2. Inflation is when most prices in an entire economy are rising. 3. There were a few months in 2009 that were deflationary. 4. They were not deflationary at an annual rate. _Source: OpenStax Principles of Macroeconomics for AP Courses 2e (CC BY 4.0), Ch 8 'Inflation'_