Background and aims:

During 10 weeks in the summer 2014 opening hours in nightclubs in Visby (Sweden) were extended by 1 hour, postponing the permitted closing time from 2 to 3 a.m. A number of preventive efforts such as Responsible Server Training, and an intensified cooperation between the police and the nightclubs were strengthened in connection with the trial. The aim of this study was to evaluate the impact of this trial on police-reported violence.

Data and methods:

To estimate the effect of the trial on violence, we compared the violence rate during the intervention period (week 24–week 33, 2014) with the violence rate in the corresponding period in Visby in 2010–2013. The intervention period thus comprised 10 weeks, and the pre-intervention period 40 weeks. As outcome measure we chose police-reported assaults that had occurred at night (midnight–6 a.m.). As control series we used assaults daytime (6 a.m.–midnight). The intervention effect was estimated with the method of “difference in differences” (DiD). Interviews with key informants provided the study with an explanatory context for the trial outcomes.

Results:

The intervention effect was strongly statistically significant with a reduction of 3.336 reported assaults at night per week compared to the pre-intervention period. This represents a decrease of 71%.

Conclusion:

The trial with an extension of opening hours at nightclubs in Visby was followed by a reduction in police-reported violence. This unexpected outcome is likely to be the result of (i) the simultaneous strengthening of efficient preventive measures, and (ii) a decreased congestion in the streets resulting from increased spread in closing hours.