Yep only 40% and I'd bet most of that 40% are over 50.
Midterm elections usually generate lower voter turnout than presidential elections. While the latter have had turnouts of about 50–60% over the past 60 years, only about 40 percent of those eligible to vote actually go to the polls in midterm elections.[1][2] Midterm elections usually see the president's party lose seats in Congress, and also frequently see the president's intraparty opponents gain power.