You might think a country founded as a penal colony would lose its enthusiasm for putting people in jail. We haven’t. Australia is locking up more people than ever. Our jails are fit to burst.

In the last year the population of Australia grew 1.4 per cent. The prison population, however, grew more than four times faster: 6 per cent.

• Ravenhall: rioters burn golf cart, ride tractor

• You won’t believe the luxuries handed to Aussie prisoners

• Needles for drugs used as ‘jail currency’

As this official chart shows, prisoners are getting lots of new cellmates to hang out with.

The normal person never goes to jail, never expects to go, and doesn’t know anybody who is in jail. We imagine everyone in jail is like the criminals from Underbelly, or like Martin Bryant.

But many of them are just idiots, not dangerous idiots. Like this guy who took an extra $17,000 of welfare benefits and thought he’d get away with it. He got a nine-month prison sentence just last week.

We are jailing more and more people even as the country gets safer and safer.

Why do we put people in jail so much?

Because the politics of it are simple.

It’s way too easy for radio ranters like Ray Hadley or Alan Jones to make sport of a magistrate that gives a sentence that doesn’t involve custody.

Shock jocks call that “letting them off scot-free.” They hoot about crims “getting away with it”.

They practically have to. That’s why they get paid thousands of dollars for every minute they’re on air. If a shock jock wasn’t calling the government “soft on crime,” the AM station would sack him and replace him with someone else who did.

The public doesn’t get to hear the experts. So politicians make policy according to the whims of populist radio announcers.

That means governments end up jailing lots of people. Like the misguided, low-IQ people who spray paint on other people’s property.

In Queensland, graffiti vandals can get seven years in the clink now.

They go in as a 22-year-old without much ability to tell right from wrong and come out as what? A 29-year-old with a bright future? Or a perpetual threat to society with a network of very dodgy mates?

In 1999 there were 14 Aussies in prison for every 10,000 people. That’s up to 19 people behind bars now.

Experts say prison is a disaster. It doesn’t deter crime. And it sure as heck doesn’t change people for the better.

Hanging out with a bunch of people who are literally all criminals it turns out, doesn’t save you from a life of crime. What a shock.

Having been locked up is actually a major predictor of committing more crime. They call that recidivism. The numbers prove it – 60 per cent of the people in custody have been in custody before.

Prison seems to turn people who made mistakes into life-long criminals. It’s no surprise. Prisons are brutal.

Some of our prisons are so dangerous even judges are hesitant to send people there.

One in every eight male prisoners in WA admitted being raped in jail, according to a study done in 2009. Other research says the rate is even higher among offenders under 25.

Australia has become a much safer country. The murder rate has plunged. As this graph shows, in 1999 there were far more murders even though we had a smaller population.

Despite the decline of violence we’re prison crazy. Even though we pay for every bar, every meal and every bunk-bed with our own taxes.

Someone might look at the graphs and say, ‘But wait! What if all that prison is what’s causing the crime to drop?’

The answer is different. There has been a global decline of violence. This is a very long-run trend, linked to economic growth.

As we get richer we behave a lot better. The homicide rate in England is estimated to be one per cent of what it was in the middle ages.

Australia has been getting richer very quickly recently and the decline of violence we see is likely because of that. Domestic violence is now a major focus – partly due to the decrease of more visible public violence.

So why all the jail time?

One reason might be Australia’s private prisons. The companies that run the prisons make more money the more prisoners there are. And they lobby governments hard.

The Catholic Prison Ministry wrote in 2014: “Handing the administration of punishment over to corporations will lead to conflict between the social interests of citizens as stakeholders and financial interests of corporations to maximise profits for shareholders.”

A 2011 report found Australia has a higher share of prisoners in private prisons than even America.

This country was founded because the jails of England were overflowing. But if our jails end up the same way, there’s nowhere for us to send people. We need to get smart about it instead.