CALL is formative in nature. The CALL system was designed to support continuous improvement--to assess, implement change initiatives, reassess, and measure change in practice data. The CALL system offers multiple ways to measure change in data over time: at the subdomain practice level and at the individual item level. 

Also, this an ideal feature to use after administering a Quick CALL survey to assess change in practice. 

The following video demonstrates how to view change in CALL data over time: