There are five times as many DNA paternity tests per capita in the US than Australia. This is not a consequence of 'technological lag', but a combination of political, cultural and economic factors. First, government agencies in the US enforce relatively more tests, at least partly because of legislative differences in the presumption of paternity. Second, government agencies in the US enforce relatively more tests partly on account of differences in family structure. More specifically, in the US there are relatively more nonmarital births, and nonmarital births are less likely to occur in the context of informal cohabitation where paternity is not in dispute. Third, differences in industry organisation account for more DNA paternity tests per capita in the US. Unlike the Australian market, the US market is characteristically divided between tests done for government agencies and those for private individuals. In turn, the private market in the US is more competitive. In particular, brokerage is pervasive, leading to more proactive marketing through the Internet, day-time television and other avenues. The study highlights the importance of social dynamics in the uptake of new technologies.