Garrett & Pakko (2009)
The Revenue Performance of Casinos was a study of the effect of a smoking ban in Illinois after their smoking ban in private casinos (July 2007) comparing those with similar casinos in neighbouring states which did not have a smoking ban in private casinos.
Comparisons were made between revenues (both for the casinos themselves, and the local government from gaming taxes,) footfall, and potential migration of customers between neighbouring states.
The revenues were used to guage whether those smokers who stayed in Illinois spent less as a result of having to go outside.
Footfall was used to guage whether smoking patrons preferred to travel out of state so they could smoke while gambling.
The use of in- and out-of-state casinos also provided controls against exceptional weather events, seasonality, and more importantly, general economic conditions.
The conclusion was that Illinois casinos lost 20% growth in 2008 after the
smoking ban while the neighbouring states grew between 3% and 6% (Figure 3 from page 32 of the report.)