Estimate, Median Age by Sex, Total Population (5-year estimate) in Marion County, IN was 34.40000 Years of Age in January of 2022, according to the United States Federal Reserve. Historically, Estimate, Median Age by Sex, Total Population (5-year estimate) in Marion County, IN reached a record high of 34.40000 in January of 2018 and a record low of 33.70000 in January of 2009. Trading Economics provides the current actual value, an historical data chart and related indicators for Estimate, Median Age by Sex, Total Population (5-year estimate) in Marion County, IN - last updated from the United States Federal Reserve on May of 2024.