RT Journal Article SR Electronic T1 Impact of US smoke-free air laws on restaurants and bars by employer size: a panel study JF BMJ Open JO BMJ Open FD British Medical Journal Publishing Group SP e018137 DO 10.1136/bmjopen-2017-018137 VO 7 IS 11 A1 Shafer, Paul YR 2017 UL http://bmjopen.bmj.com/content/7/11/e018137.abstract AB Objectives Thirty states have smoke-free air laws that ban smoking in restaurants and bars, covering nearly two-thirds of the US population. It is well established that these laws generally have a null or positive economic impact on restaurants and bars. However, all establishments in a geographic area are usually treated as a homogeneous group without considering the potential for differential effects by establishment characteristics. This study uses variation in smoke-free air laws over time to estimate their impact on employment in restaurants and bars with a focus on potential differences by employer size (number of employees). A two-pronged approach with a national-level and state-level analysis is used to take advantage of more granular data availability for a single state (North Carolina).Design Observational study using panel data.Setting 1) US, 2) North CarolinaInterventions Smoke-free air laws.Outcome measures State-level accommodation and food services employment for all 50 states and District of Columbia from 1990 through 2014 (Quarterly Census of Employment and Wages); county-level restaurant and bar employment in North Carolina from 2001 through 2014 (North Carolina Department of Commerce).Results There is no evidence of a redistributive effect of smoke-free air laws on restaurant and bar employment by employer size.Conclusion The lack of a redistributive effect is an important finding for policy-makers considering implementation or expansion of a smoke-free air law to protect employees and patrons from the dangers of exposure to secondhand smoke.