Research on a migration lottery allowing Tongans to move to New Zealand found that the lottery winners saw a 263 % increase in income from migrating (after only one year in New Zealand) relative to the unsuccessful lottery entrants. A longer-term study on the Tongan lottery winners finds that they "continue to earn almost 300 percent more than non-migrants, have better mental health, live in households with more than 250 percent higher expenditure, own more vehicles, and have more durable assets". A conservative estimate of their lifetime gain to migration is NZ$315,000 in net present value terms (approximately US$237,000).