Mass attendance events are a mainstay of economic and social activity. Such events have public health consequences, facilitating the spreading of disease, with attendant economic consequences. There is uncertainty over the impact such events can have on the spread of disease. We investigate the impact of regular mass outdoor meetings on the spread of a virus by considering football matches in England in February and March 2020 and the spread of Covid-19 into April 2020. There were 340 league and cup football matches with a combined attendance of 1.625m people in March, taking place over 188 of 313 local areas. We look at the occurrence and attendance at matches, and how full the stadia were, and how these variables are related to the spread of Covid-19 in April. We evaluate Covid-19 cases, deaths and excess deaths, all as rates of 100,000 people in an area. We find evidence that mass outdoor events were consistent with more cases and deaths, even after controlling for measurable characteristics of local areas. We find that a football match is consistent with around six additional Covid-19 cases per 100,000 people, two additional Covid-19 deaths per 100,000 people, and three additional excess deaths per 100,000 people. This effect is slightly stronger for the areas of away teams in March, and slightly weaker for matches in February. These results suggest caution in returning to unrestricted spectator attendance at matches. We caveat our analysis though by noting that stadium access and egress routes can be adapted such that some of the opportunities for the spread of an airborne virus could be mitigated. We recommend that the relevant authorities conduct pilot events before determining to what extent fans can return to mass outdoor events.

It is conventional wisdom that collusion is more likely the fewer firms there are in a market and the more symmetric they are. This is often theoretically justified in terms of a repeated non-cooperative game. Although that model fits more easily with tacit than overt collusion, the impression sometimes given is that 'one model fits all'. Moreover, the empirical literature offers few stylised facts on the most simple of questions -how few are few and how symmetric is symmetric? This paper attempts to fill this gap while also exploring the interface of tacit and overt collusion, albeit in an indirect way. First, it identifies the empirical model of tacit collusion that the European Commission appears to have employed in coordinated effects merger casesapparently only fairly symmetric duopolies fit the bill. Second, it shows that, intriguingly, the same story emerges from the quite different experimental literature on tacit collusion. This offers a stark contrast with the findings for a sample of prosecuted cartels; on average, these involve six members (often more) and size asymmetries among members are often considerable. The indirect nature of this 'evidence' cautions against definitive conclusions; nevertheless, the contrast offers little comfort for those who believe that the same model does, more or less, fit all.

This paper estimates the implicit model, especially the roles of size asymmetries and firm numbers, used by the European Commission to identify mergers with coordinated effects. This subset of cases offers an opportunity to shed empirical light on the conditions where a Competition Authority believes tacit collusion is most likely to arise. We find that, for the Commission, tacit collusion is a rare phenomenon, largely confined to markets of two, more or less symmetric, players. This is consistent with recent experimental literature, but contrasts with the facts on 'hard-core' collusion in which firm numbers and asymmetries are often much larger. JEL Classification codes: L13, L41

This paper estimates the implicit model, especially the roles of size asymmetries and firm numbers, used by the European Commission to identify mergers with coordinated effects. This subset of cases offers an opportunity to shed empirical light on the conditions where a Competition Authority believes tacit collusion is most likely to arise. We find that, for the Commission, tacit collusion is a rare phenomenon, largely confined to markets of two, more or less symmetric, players. This is consistent with recent experimental literature, but contrasts with the facts on 'hard-core' collusion in which firm numbers and asymmetries are often much larger. JEL Classification codes: L13, L41

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