noun
infant mortality rate
A demographic statistic measuring deaths of children under one year old per 1,000 live births.
この国の幼児死亡率は年々低下している。
The infant mortality rate in this country is declining year by year.
死亡率 is the general mortality rate, while 幼児死亡率 specifically refers to infants.
Compound of 幼児 (infant) + 死亡率 (mortality rate).