Samples of data sources for measuring this outcome:
Diabetes rate decreases

Data source

CDC - U.S. Diabetes Surveillance System
National level resources - Click on "Table" for national median.
State level resources - Hover mouse cursor over state of interest.
County level resources - Select a state in box under the "Explore the Data" heading on the right.
CDC 500 Cities Project - Diagnosed diabetes among adults age 18+ years
City level resources - Under View Data by Measure, use the category and measure drop-down menus to select "Health Outcomes" and "Diabetes."