Which is exactly why our government leaves the door wide open.
If Japan was truly worried about fortifying their plummeting population, I think they would first consider pulling in low wage workers from other predominately light complected asian nations, such as Thailand, Hong Kong or the Philipines.
In addition to getting ALL of the illegals out, we need to figure out how to get the idle poor percentage down to an affordable level. Regardless of the age.
If taxes where lower and society was more welcoming to larger families, we would have more large families of 4 , 5 6, or more children. As it is, present societal concerns and government policies make it difficult to maintain a middle-class lifestyle on one income.
Today everyone lives for themselves and the present, not the future or others. Having children is a bet for the future.