Coalitions allow potential entrants to pool resources, share the upfront cost of attempting entry, and enhance the likelihood of successful entry.
Coalitions enhance social welfare if they enable joint entry when independent entry is infeasible.
If independent entry is feasible, coalitions can diminish social welfare by reducing future competition. We construct a forward looking measure of industry concentration, the expected Hirshman-Herfindahl index. Analysis shows that coalitions among entrants in industries with few incumbents and high probability of entry should face regulatory scrutiny. The model is illustrated through case examples of entry coalitions in the long distance telecommunications and cable industries.