Australia-wide, Aborigines are 2.8 per cent of the population, but make up about 29 per cent of the prison population. Nearly 50 per cent of juveniles in custody are Aboriginal, a reminder to everyone that the zenith of the stolen children phenomenon is now, after Kevin Rudd apologised on our behalf for the practice.

These proportions have not much changed over the years. The numbers of Aboriginal prisoners rose in step about 20 years ago when opportunistic politicians such as Bob Carr, then New South Wales premier, decided getting ''tough on crime'' by doubling the imprisonment rate was a good way to win the approval of Alan Jones. Jail populations virtually doubled, and sentences increased.

In recent, more liberal, years the prison population has declined slightly, but is still more than 80 per cent higher than 30 years ago. The proportion of Aborigines in the system has been fairly constant.

This is not primarily because police discriminate against Aborigines, or because magistrates and judges are more likely to send Aboriginal children or adults to jail, and for longer than non-Aborigines, although it is always possible to find cases of differential treatment.

Even in soft, tolerant and liberal Canberra, where the general imprisonment rate is lower than elsewhere, there are apparently disproportionate jail rates, with an indigenous person about 13 times more likely to be in custody than representation would suggest.

Here, as elsewhere in Australia, imprisonment rates reflect membership of the underclass. Aborigines are massively overrepresented in jail primarily because they are massively overrepresented in the underclass.

Canberra has a big indigenous middle class. Its members are no more likely to go to jail than other members of that class. Throughout Australia, the chance of a 30-year-old-man with a job and matriculation going to jail are about one in 3000; for a woman, about one in 15,000.

But we also have a sizeable indigenous population consisting of those essentially out of the economic and mainstream social system. These may be only about 1.5 per cent of the population, but they amount to about 20 per cent of the Canberra underclass - the main well from which the prison and youth custody population is drawn.

Even the word ''underclass'' is pejorative in imputing a blame on its membership. The underclass consists of families in which the men, if there are any immediately about, do not regularly work. In which there are patterns of intergenerational dependence on welfare. In which educational standards and aspirations have been low, a problem compounded by an increasing scarcity of low-skilled work. In which home environments do not much value education, or, some would say, disapprovingly, a work ethic.

From the point of view of those inclined to be morally sniffy, those in the underclass tend to be more likely to have children without being in permanent relationships, or to have children by different fathers, and to have children earlier.

It is hardly surprising that more members of the underclass have health problems, including mental health problems, and that a larger-than-average proportion consume too much alcohol and drugs, including cigarettes.

More than mere poverty is involved: aged pensioners are often poor but not generally regarded as members of the underclass. Nor are families in which there is a pattern of fairly regular work, even if the pay is supplemented by social welfare benefits. It is of the essence of being thought a member of this underclass that one is marginalised from, or excluded from, the broader community, and that one finds it almost impossible to get in.

Being black is not the primary problem, but often doesn't help. The underclass is a collective of those most marginalised and least able to control the factors that affect their lives: their lot has been made more miserable in more recent times as politicians, even of the left, have ''permissioned'' commentators to argue that most of their problems are of their own making, whether from fecklessness, indolence, want of ambition or failure to take advantage of generous schemes provided by the ''system''.

Such people are far more likely to commit crime, and get caught, or otherwise to attract the ire of society's guardians, who are not merely the police but the social welfare establishment, the educational establishment and Centrelink. All are tasked with reforming or saving an underclass they do not understand.

Much crime within the group - particularly violence against women and children - goes relatively unnoticed. But crime against ''ordinary'' Australians is greatly to be deplored, and, when it occurs, more severely punished than when committed by members of the mainstream, who, after all, face their own pressures to reform.

This is so with crimes against property - including housebreaking and ''borrowing'' cars - and crimes against good order, such as hanging around, being drunk or under the influence of drugs, begging or ''humbugging''.

Some of the ''crime'' is almost an incident. In the Northern Territory, for example, a supposed epidemic of child sexual abuse created an intervention which saw many more police in Aboriginal communities.

These have failed to find the hundreds of paedophiles said to be everywhere, but their mere constant presence has had a marked effect in reducing violence, drunkenness and vandalism. Alas, the devil finds work for idle police, so the main form of visibility now involves stopping cars and fining people for driving unregistered ones, failing to use seatbelts and so on. Jail populations have increased because people cannot afford to pay fines, but police are stolidly persisting, thinking that these silly people will one day understand that they must obey the same rules as everyone else.

In much the same spirit, a Centrelink official accused me of wanting different rules for Aborigines when I suggested to him that doing assets tests in remote communities was a cruel travesty. In the particular case, the illiterate person, with not much English being given the Centrelink ''business'' was a mother of children stranded because her husband was in clink cutting out a traffic fine.

The problem of the underclass is not necessarily that, as Jesus and Tony Abbott said, ''The poor are always with us.'' Nor is it that they need more welfare benefits, or more of Jenny Macklin's tough love. It is that their lives and circumstances are quite different from those imagined in the offices of people such as Bill Shorten, and are not going to be transformed by the programs, or the rules, or even the penalties, devised by them.

The past five years has seen steady national growth and more spending on health, educational and social security, not least in Aboriginal affairs. But this has failed to reduce the size of the underclass, or to make a difference to the lives of its most prominent denizens.

What a commentary on a Labor government that it spent billions to leave the nation's most vulnerable children further behind.

>> Jack Waterford is editor at large. jack.waterford@canberratimes.com.au