The Patient Protection and Affordable Care Act, passed in March 2010, allows young adults to stay on their parents’ health insurance.  Recently Akosa Antwi, Moriya, and Simon (2013) argue that this provision causes significant labor supply effects.  Using both SIPP and CPS data, I estimate models over several “placebo” dates.  I show that difference-in-difference regressions with these dates also produce statistically significant “effects” long before the ACA was implemented.  This suggests that the effects that have been attributed to the ACA actually reflect overall dynamics in the age-structure of the labor market. (JEL I13, I18, J08)