The latest labour force figures highlight how great a problem underemployment has become in our economy. While policies such as jobkeeper may artificially keep the unemployment rate low, polices that seek to reshape the post-virus economy must address underemployment.

The 1 percentage point rise in unemployment rate in April from 5.2% to 6.2% was a massive shift – the highest ever one-month rise. And yet because those people with access to jobkeeper remained classed as employed even though they may not be working, and because a large number of people left the labour force entirely, the rise was nowhere as large as expected.

It wasn’t even overly astonishing in a historical sense. The 1 percentage point jump was a record, but it only just beat the previous record of 0.9 percentage points set during the 1982 recession. It certainly didn’t break the scale – unlike underemployment.

Underemployment jumped from 8.8% to 13.7% – a 4.9-percentage point jump that dwarfed the previous record one-month increase of 0.8 percentage points set during the 1990s recession.

A graph shows just how poor the unemployment rate is at portraying the state of the economy. The current unemployment rate is not even the highest in the past decade; the current underemployment rate is the highest of all-time by a scarcely believable amount:

There are two types of underemployment – those who would like to have more hours than they currently work and those who have had their hours reduced due to economic reasons. As a general rule the first category makes up around 90% of all underemployed workers.

In April the number of those who just preferred to work more hours barely changed, but the number of those who were underemployed due to economic reasons increased by 400%:

The importance of underemployment can be seen when we look at how it changed in April, along with unemployment, for those over 45.

Rather bizarrely the unemployment rate for women over 45 actually fell in April – there were actually 6,800 fewer women unemployed in April than in March! It’s not that they were no longer unemployed because they got a job, but because they were no longer even looking for work.

The most obvious reason is that these women likely have children of school age and were staying at home to look after them and help them with their online learning. But even while men over 45 did see an increase in unemployment it was nowhere near as large as the 85% increase in the number of underemployed:

Across all age groups and genders, the jump in underemployment was more than double that of unemployment:

And while the increase in underutilisation (the combination of both categories) was largest among younger workers, this was more a factor of their relative lack of connection to the workforce than them being particularly targeted.

Given casual workers needed to be with an employer for more than 12 months to qualify for jobkeeper and because younger workers are less likely to be able to clear this rather absurd hurdle, it meant they were always going to be more likely to lose their job than older workers.

But the rise in underemployment is most pronounced among workers in the late 20s through to their 40s. Among men aged 25-44, the number of underemployed more than doubled.

Now all of this might seem like a bit of a dive into the weeds of the labour force, but the problem is underemployment has for the past six years been a growing issue:

It used to go up and down in line with unemployment but even before the April figures came out the two measures were further apart than ever before.

And yet the treasurer, Josh Frydenberg, is not focused on the issue. There was no mention of it in his economic statement to parliament last Tuesday, nor in the press conference announcing the April labour force figures.

Last month when Nine’s Shane Wright asked him if he had any estimates for underemployment similar to the treasurer’s estimate that unemployment would reach 10%, he dodged the question and instead replied that replied “our focus has been from Treasury on that unemployment headline number”.

And when your focus is one number you inevitably come up with a policy to keep that number low – which is what jobkeeper has done.

But the clear lesson of history is that fewer men work full-time after recession than before and underemployment increases:

And this shift is part of moves towards greater workplace “flexibility” after recessions, all under the guise of economic recovery.

The prime minister this week told the Australian that “employees will be asking for a more flexible workplace … it works both ways, it’s a two-way street”. Such an attitude suggests the push for even more flexible arrangements (around the ability to hire and fire and reduce hours) will be advocated as part of a nebulous compromise with workers who will need greater flexibility purely to deal with the health crisis.

Already the government has shown its hand on what it means by a “two-way street” with new regulations that reduce the consultation period for changes to work agreements such as cuts to pay, penalty rates, leave entitlements and changes to ordinary hours of work from one week down to 24 hours.

Such moves are designed to do one thing – keep wages down by having workers worry about keeping their hours rather than bargaining for higher wages, and it inevitably leads to higher levels of underemployment.

The government knows the unemployment rate gets the headlines, and so it has devoted its focus to keeping that down. But underemployment will be the measure that lets us know when (and if) we have recovered from this crisis, and whether the post-virus economy is one of low wages and income growth or higher underemployment driven by “flexibility”.

• Greg Jericho writes on economics for Guardian Australia