Japan has the dubious title of the oldest society in the world, with one in four of its citizens past the age of 65. And while the image of the elderly is typically of sweet grandparents, in Japan, senior citizens are committing petty crimes like shoplifting in bigger numbers than teenagers.

Inside the office of a private security firm in Tokyo are video monitors that take up the entire wall, bisected into 16 boxes showing various camera angles on a nearby business.

Mochizuku Morio shows us a live feed of a grocery store that's a few blocks away. He and his private security company are hired by stores across Japan to consult on crime prevention tactics, and if needed, to add some extra electronic eyes on their shops. So he's seen firsthand the trend taking hold over the past few years.

"Baby boomers are the ones that commit crimes these days," he says. "Shoplifters are grandmas and grandpas in their 70s and 80s."

Sharp rise in crime by the elderly

Arrests of Japan's elderly for criminal offenses have doubled in the past decade — from an average of 80 per 100,000 residents between 1995 and 2005 to 162 per 100,000 residents between 2005 and 2015, according to the National Police Agency. Morio has his theory: "They were brought up during and after the war, and they had to survive, and they have less conscience, they feel less guilty."

Across town, Yuki Shinko, researcher and author of a book called Old People Underworld,says that's an unfair generalization. Shinko attributes some of the crimes to dementia or side effects of medications. But more importantly, she says, seniors today are isolated and bored.

"[There's a] sort of moral corruption that happens as a result of their anxiety, stress and anger that they feel the need to relieve in some form," Shinko says.

Japan is one of the few countries in the world where the old outnumber the young. Here, more adult diapers are sold than baby diapers. If nothing changes demographically, by the year 2060, people aged 65-plus will make up at least 40 percent of the population.

And seniors are largely living alone, isolated from a sense of community and personal worth. While petty crimes make up the majority of those committed by the elderly, the national police statistics show murder and assault are rising.

"Our image of old people is that they slowly wither away. But I feel like it's the exact opposite right now. They are so young at heart and they have so much energy, but there is no place to shine and they feel like they have all these things going to waste," says Shinko.

Thousands of them are winding up in prisons. National police figures for 2015 show the number of people age 65 and older arrested for criminal offenses makes up 20 percent of all arrests, which totals nearly 48,000.

The Japanese government is spending tens of millions on constructing prison wards specifically designed to cater to a growing number of elderly inmates. But Shinko warns that nicer prison facilities might have the opposite effect of deterring crime.

If you steal and get away with it, you may end up with free groceries or money. But "If you are arrested, you still get a roof over your head, you're fed three times a day and you get health checkups. So it's sort of a win-win situation either way," says Shinko.

It's a vexing policy problem for Japan, and a glimpse of yet another difficult challenge as more and more of its population ages past retirement.

Chie Kobayashi contributed to this story.

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