Before revision:  Using the data from the National Health Interview Survey (NHIS) , we apply this  identification strategy to evaluate the causal effect of the Affordable Care Act (ACA) on  health care access and utilization of old Americans.
After revision:  Using the data from the National Health Interview Survey (NHIS) , we apply this new identification strategy to evaluate the causal effect of the Affordable Care Act (ACA) on health care access and utilization of old Americans.