english: Lant Pritchett explains this notion in details in his book: Let Their People Come: Breaking the Policy Deadlock on International Labor Mobility. He quotes the results of a study claiming that:
non_english: Lant Pritchett spiega il concetto in modo dettagliato nel suo libro (del 2006): Let Their People Come: Breaking the Gridlock on International Labor Mobility, nel quale cita i risultati di un'apposito studio, sostenendo che: