The total rate increased to 1.46 in 2015, slightly up from the previous rate of 1.42 in 2014, according to the health ministry.

The biggest contribution to the increase came from women 30 to 34, according to Bloomberg.

This is no doubt a good sign for a country struggling with a looming demographic crisis.

But what's particularly interesting about this spike in fertility is that there was a correlation with cash incentives for new parents.

Christopher Wood, author of CLSA's weekly Greed & Fear newsletter, pointed out in his latest installment that the highest fertility rate among Tokyo's wards was in the Minato Ward, where parents get one-time cash payouts of up to 180,000 yen — about $1,684 — a birth.