In response to increasing health expenditures and a high number of physician visits, the
German government introduced a copayment for ambulatory care in 2004 for individuals
with statutory health insurance (SHI). Because persons with private insurance were
exempt from the copayments, this health care reform can be regarded as a natural
experiment. We used a difference-in-difference approach to examine whether the new
copayment effectively reduced the overall demand for physician visits and to explore
whether it acted as a deterrent to vulnerable groups, such as those with low income or
chronic conditions. We found that there was no significant reduction in the number of
physician visits among SHI members compared to our control group. At the same time,
we did not observe a deterrent effect among vulnerable individuals. Thus, the copayment
has failed to reduce the demand for physician visits. It is likely that this result is due to
the design of the copayment scheme, as the copayment is low and is paid only for the first
physician visit per quarter