the best way to help increase birth rates: every japanese m - japanese f who has 3 children should be entitled to a 150 square meter house or apartment (considering a ration of 30 square meters per person as a comfortable metric) that would increase japanese nationals, cut immigrants and improve the economy with government housing plan and infrastructure. to pay for this you simple cut all the retirement, it's just creating a snowball effect, if eventually the population reaches a high point and you want to stop the growth, give back the retirement and stop the 3-kids house/apartment plan.
Brazil