One of the first responses that many governments enacted during the coronavirus pandemic was limiting or banning mass gatherings like sporting events, concerts, conferences, and weddings. But how effective were those measures in reducing the number of coronavirus infections and subsequent mortality? In a recent article by Alexander Ahammer, Martin Halla, and Mario Lackner (all Johannes Kepler University), published in the journal Contemporary Economic Policy (open access), we get an answer. Ahammer et al. make use of a cool natural experiment:
We quantify how NBA and NHL games have contributed to the early spread of COVID‐19 in the United States... We analyze how much games held between March 1 and March 11 have contributed to the community spread of COVID‐19 in counties surrounding NBA and NHL venues. Since the game schedules were determined long before the first COVID‐19 case became public, their spatial and temporal distribution should be unrelated to the initial spread of COVID‐19 in the US...
Specifically, Ahammer et al. look at how the number of NBA and NHL games (combined) between 1-11 March 2020 relate to the cumulative number of coronavirus cases and deaths as of 30 April 2020 (6-8 weeks later) in the county that hosted the games, or neighbouring counties. They find that:
...that each additional mass gathering between March 1 and 11 increased cases by 269 per million and deaths by approximately 15 per million population. These are substantial effects. Compared to the average case and death rates across the counties in the data, our estimates correspond to increases of 9.2% and 10.3% per game, respectively. Both estimates are statistically significant at the 1% level.
When they run separate models for cumulative cases (and deaths) as at each day from 13 March to the end of April, where:
...we expect effects to be strongest around 3 weeks after the shutdown. This is precisely what we find. The effect of games starts to pick up around March 19 and increases at a decreasing rate since then. This is true for both cases and deaths. Furthermore, we see that cases respond sooner than deaths, which makes sense given the natural lag between diagnosis and death. In terms of magnitudes, estimates for COVID‐19 deaths (cases) range between 0.002 (0.367) on March 13 and 15.195 (269.131) on April 30.
And, in case you're wondering:
If we split our treatment variable and count NBA and NHL games separately, we find that games in both leagues positively affect COVID‐19 spread...
Finally, when they stratify their analysis, they find that:
These effects are larger in densely populated areas and in colder regions.
No surprises there. The obvious conclusion overall is that limiting or banning mass gatherings was an effective strategy in arresting the spread of coronavirus. Ahammer et al. conclude that:
...banning indoor mass gatherings has an enormous potential to save lives. This is especially important given that such measures are relatively easy and cheap to implement.
Their results don't necessarily extend to outdoor gatherings, but at least we have some surety now of the effectiveness of one of the early tools that governments employed during the pandemic.
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