(Newser) – Hot stock tip: the market for "incontinence products" in Japan is a $1.4 billion-per-year industry, and it's growing at 6-10% a year, thanks to the country's aging population, reports Japanese newspaper Nikkei, per Quartz. Japan has the highest percentage of people over the age of 65 in the world, and adult diapers are set to outsell baby diapers by the year 2020, according to the country's biggest diaper maker. Added bonus? You can charge 2.5 times more for the adult versions. (Read more weird news stories.)