A 0.2 gap for births, a 2.0 gap for deaths
In 2023, the crude birth rate was 6.8 per 1,000 in Fukuoka Prefecture and 6.6 in Kumamoto Prefecture. The crude death rates were 12.4 and 14.4, respectively. Fukuoka's birth rate was 0.2 higher; Kumamoto's death rate was 2.0 higher. The counts cover births and deaths of Japanese people occurring in Japan, assigned to a prefecture by the child's or deceased person's residence. The denominator is the Japanese population as of 1 October 2023.
Total fertility rates reverse the ranking
The same vital-statistics table gives a total fertility rate of 1.26 for Fukuoka and 1.47 for Kumamoto: Kumamoto ranks higher on this measure. The total fertility rate sums age-specific birth rates for women aged 15–49, unlike the crude birth rate, which divides births by the whole Japanese population. The reversal is not a contradiction, but these figures alone cannot establish a single cause for it.
Explaining the death-rate gap
Crude death rates are not adjusted to a common age structure. Populations with different age profiles can have different overall rates even if mortality risks at each age were identical. Explaining Kumamoto's higher rate requires age-specific population and mortality data for a matching period; the crude rates alone cannot establish a difference in health or health-care quality.