Working out what's happening in the jobs market is trickier than you may think - and has just got trickier. On the face of it, this week's figures from the Bureau of Statistics are simple: they show employment grew by a bit more than 10,000 last month and the rate of unemployment was steady at 5.4 per cent.
But it's not that simple. The rate at which people of working age participated in the labour force (either by holding a job or actively seeking one) fell from 65.1 per cent to 65 per cent of the labour force.
At times like these, with the growth in employment slowing and the number of job vacancies falling, a decline in the participation rate is usually taken as a sign the number of "discouraged jobseekers" is rising. These are people who'd like to work but who, believing there are no jobs available, have stopped actively seeking one, meaning they're no longer counted as unemployed.
So, many economists would take the fall in the participation rate last month to mean the jobs market deteriorated despite the unchanged rate of unemployment.
But if we want to play this game we should really start two years ago, in January 2011, when (using the trend figures) the unemployment rate reached a low of 5 per cent. Since then it's risen only to 5.4 per cent, which doesn't seem much.
Over the same period, however, the "part rate" has fallen from a peak of 65.8 per cent to 65 per cent. Saul Eslake, of Bank of America Merrill Lynch, calculates that had this decline not occurred, all else being equal the unemployment rate in December last year would have been 6.6 per cent, not 5.4 per cent.
Fortunately, however, it's still not that simple. Heard of the ageing of the population? Whereas for decades it was pushing our participation rate up, it's now started pushing it down, meaning it's no longer safe to assume a fall is all the work of discouraged jobseekers.
This is an unfamiliar but important story, so settle back for a primer on demography.
We are living at a time in the world's long history when longevity is steadily rising (because of improvements in public health, increasing affluence and advances in medical science) but fertility is falling (because of improvements in contraception and rising affluence). A country's "total fertility rate" is the average number of children women are projected to bear over their lives.
As The Economist magazine has explained, when a country's fertility rate falls sharply, the children born before the fall become "a sort of generational bulge surging through a society".
In the case of the developed countries, the sharp and continuing fall in fertility was caused by the advent of the contraceptive pill, and the surging generation became known as the baby boomers. But something similar happened a few decades later in those developing countries that began developing rapidly. Access to contraception improved, girls became better educated and families decided to have fewer children.
A country in this situation enjoys a "demographic dividend". After a while, the earlier generation becomes old enough to be part of the labour force (they reach the age of 15) and this happens while old people are dying fairly early and fewer babies are being born.
So the country enjoys a big improvement in its "dependency ratio" - the ratio of people who are dependent on others for their living (because they are either too young or too old to work) to those of working age (which is often defined as everyone over 15, but for these purposes should be limited to those aged 15 to 64).
The decrease in the dependency ratio - that is, the increase in the number of potential workers relative to the number of people they have to support - is the demographic dividend. It means a country can grow faster and become richer (measured as income per person) - provided you can find jobs for all those who want to work.
The dividend continues for several decades and actually gets bigger as the bulge generation enters the "prime working age" of 25 to 54. It has helped keep our participation rate rising and thus made a significant contribution to Australia's rate of economic growth for the past 30 or 40 years.
Can you see where this story is heading? Eventually, the demographic dividend becomes a negative as the bulge generation continues to age and eventually starts retiring. As Dr David Gruen of Treasury put it last year, the tail-wind of the past becomes the head-wind of the future.
When a baby boomer stops working, the working population falls by one and the dependent population increases by one, meaning the bulge of baby boomers produces a rapid deterioration in the dependency ratio.
It also means we should see a decline in the participation rate as more of the population moves from the age range where they're highly likely to be working to one where they're much less likely to be working.
The first baby boomers were born in 1946, which was 67 years ago. The last were born in 1964, which was 49 years ago.
So by now you'd expect to see the participation rate falling for reasons that are completely demographic and have nothing to do with the state of the economy and the jobs market.
Sorry, one more complication. We've known for some years that the trend to early retirement has reversed and more older workers are delaying their retirement or finding ways to keep working for a few days a week.
In other words, some baby boomers aren't retiring as expected - maybe because they're not feeling old and tired or maybe because they haven't saved enough to allow them to retire in the comfort to which they've become accustomed.
Obviously, to the extent this is happening it's working to counter the purely demographic decline in the part rate. So what is happening?
The econocrats have done some figuring which shows that, over the year to December, ageing contributed minus 0.3 percentage points to the participation rate, while the trend to delay retirement contributed plus 0.1 percentage points.
In other words, the demographic dividend has reversed, although it's being partly offset by the trend of some baby boomers delaying their retirement.
So most but not all of the overall fall in the part rate can be regarded as a rise in hidden unemployment.