Towards the end of ABC TV’s special “Sovereign Borders“ edition of Q&A last week came an intriguing but frustrating back-and-forth about the number of migrants Australia welcomes each year.

The key protagonists were Shen Narayanasamy, GetUp’s human rights campaign director, and retired general Jim Molan, co-author of the Coalition’s refugee and asylum policy and Tony Abbott’s former special envoy for Operation Sovereign Borders.

As the transcript reveals, the two speakers offered up very different numbers for Australia’s annual migration intake:

SHEN NARAYANASAMY: I think there is an alternative [to Operation Sovereign Borders] because when you understand that we take 800,000 people a year and we have done so since prime minister John Howard, the highest intake in history, it’s because we know it turbo-charges our economy and contributes to our society.

JIM MOLAN: 800,000 per year?

SHEN NARAYANASAMY: 800,000 per year.

JIM MOLAN: 200,000 per year.

SHEN NARAYANASAMY: No, 800,000.

JIM MOLAN: 200,000 per year.

SHEN NARAYANASAMY: This is the problem.

JIM MOLAN: 200,000 per year.

At this point, UNSW law professor and refugee expert Jane McAdam intervened in an attempt to clarify matters. She suggested that the two figures could be reconciled: Molan was referring to Australia’s annual intake of 200,000 permanent migrants, while Narayanasamy was including an additional 600,000 temporary migrants.

Neither of the two protagonists threw much light on the issue; in fact, the exchange probably only added to the level of public confusion, despite McAdam’s attempt to reconcile the figures. This was surely not the panellists’ intention. But combative, live television is not the best place to discuss statistics, particularly when they are complex. Counting the number of migrants Australia takes in each year might appear simple, but it is not really so straightforward.

All three panellists were correct in their own terms: Australia’s annual permanent migration intake is capped at just below 200,000 people (Molan’s figure) and each year around 600,000 migrants are granted temporary visas as international students, working holiday makers or temporary skilled workers (McAdam’s figure). Adding these two numbers together gives the total of 800,000 (Narayanasamy’s figure). But there are two serious problems in counting migration numbers in this way.

The first is that there is a big difference between the number of visas granted in any one year and the number of migrants who actually arrive. Many people granted visas are already in Australia, renewing an existing visa or shifting between different visa classes. Each time this occurs, no additional person enters Australia. They may be changing their status — which can have significant implications — but this doesn’t change the number of people who are coming and going across the frontier.

We know, for example, that almost half of Australia’s permanent migration program consists of people who are already here, generally on some kind of temporary visa. In 2015–16, 190,000 permanent skilled and family visas were granted, of which more than 91,000 went to people already in Australia. To include these people in the number of migrants Australia “takes” in a financial year is to engage in double counting.

The same issue arises in relation to temporary migrants. At least 100,000 of the people granted temporary visas in 2015–16 were transferring from one type of temporary visa to another: 36,000 working holiday makers obtained a second 12-month working holiday visa; and about 73,000 international students moved to a different type of study visa (from an English-language course to university entry, for example), or to a 485 post-study work visa, a 457 temporary skilled work visa or a working holiday maker visa. There are also other movements across and within visa classes (when working holiday makers become students, for instance, or 457 visa holders renew their work visas). Again, since all these migrants are already present in Australia they can’t be included in the national annual “intake” without double counting.

If we exclude these two groups, then the number of visas issued to permanent and temporary migrants arriving in Australia from another country in any one year would fall below 600,000.

There is an added complication: the need to account for New Zealanders on “special category visas”. Under the Trans-Tasman Travel Arrangement, New Zealanders can enter Australia freely, to live and work for an indefinite period, and they aren’t included in the migration program statistics. We can set the New Zealand issue aside, however, because it is part of the second, more significant issue we face in counting Australia’s annual net migrant intake: the fact that hundreds of thousands of people also leave Australia every year.

Many students, working holiday makers, international students and 457 visa holders go home at the end of their travels, their studies or their employment contracts. Some permanent residents and citizens also live outside Australia for extended periods, returning to previous countries of residence, pursuing job opportunities or following their hearts or their study goals.

So any meaningful attempt to quantify Australia’s annual migrant “intake” must also reckon with the number who depart — at least as long as our intention is to get a handle on the nation’s capacity to manage the impact of migration flows on such things as the demand for housing, jobs, transport, healthcare and government services.

After years of trying different measurements, the Australian Bureau of Statistics has settled on a methodology for counting migrants that takes account of both arrivals and departures while excluding short-term visitors like tourists. If you’re in Australia for 12 out of 16 months, you’re included; if you aren’t, you’re not. This enables the ABS to come up with a figure for net overseas migration, or NOM, which is critical to understanding why Australia can’t be said to be taking 800,000 people a year.

The big difference between the number of visas granted in any one year and the number of people who are in Australia for at least 12 months in a 16-month period, was neatly visualised in the Productivity Commission’s recent report, Migrant Intake into Australia:

howmanymigrants

Source: Productivity Commission, Migrant Intake into Australia, figure 12.3, page 416

The commission’s chart shows the many different migration pathways, including arrival on a temporary or permanent visa, the granting of onshore visas to people already here, departure or progression to citizenship. These are key to understanding why the number of visa grants doesn’t tell us how many people are arriving. The chart shows, for example, that 298,000 migrants came to Australia on temporary visas in 2013–14, yet in that year there were almost twice as many temporary visas issued (292,060 international student visas, 98,570 skilled worker visas, and 183,428 working holiday visas).

So exactly how many migrants does Australia take each year in net terms — that is, if we deduct departures from arrivals and exclude short-term visitors like tourists? In 2014–15, the ABS estimated the total was 168,200.

*Read the rest at Inside Story

* Henry Sherrell is a research officer with a focus on labour mobility and migration at the Australian National University. Peter Mares is a contributing editor of Inside Story and author of Not Quite Australian: How Temporary Migration Is Changing the Nation.