A public health team in Delhi conducts a survey on January 1st, 2024, to estimate the burden of diabetes in a population of 50,000. They identify 2,500 individuals with diabetes (both newly diagnosed and previously known cases). Six months later, on July 1st, 2024, they conduct a follow-up and find 200 new cases of diabetes in the remaining disease-free population. Which investigation/measure would be most appropriate to assess the risk of developing diabetes in the disease-free population during this 6-month period?