According to one group of scholars, one-child limits had little effect on population growth or the size of the total population. However, these scholars have been challenged. Their own counterfactual model of fertility decline without such restrictions implies that China averted more than 500 million births between 1970 and 2015, a number which may reach one billion by 2060 given all the lost descendants of births averted during the era of fertility restrictions, with one-child restrictions accounting for the great bulk of that reduction.