And it appears the state's housing affordability and availability crisis might be a factor driving increased numbers of younger working age people away.

The state already had the nation's oldest population by average before the coronavirus pandemic.

Trends revealed in net interstate migration figures for 2020-21 released during the week by the Australian Bureau of Statistics have demographer Lisa Denny concerned Tasmania's greying will accelerate.

Broadly, they showed significant net losses of younger people of working age to the mainland, a reversal of the pattern from previous years

For example, Tasmania lost 310 more people aged 25-29 to the mainland than it gained from the mainland during the financial year.

It had made net gains in that age group of between 250 and 370 in the preceding four financial years.

Similarly, Tasmania lost a net 310 people aged 30-34 to the mainland, after gains ranging between 170 and 350 on the previous four years.

Net interstate migration also went into reverse for 35-39-year-olds (negative 40) after gains between of 240 and 290 in each of the previous four years.

The state also lost a net 380 people aged 20-24, although that was similar to previous years.

By contrast, it gained a net 200 people aged 50-54, 330 aged 55-59, 230 aged 60-64 and 120 aged 65-69.

Dr Denny believed worsening housing affordability could be a factor, particularly for younger working age people who tended to be less well paid than older ones.

"Perhaps border closures and family may also have an influence during the pandemic," she said.

"Research out of the Centre for Population suggests that house prices have a greater impact than unemployment rate."

In a blog post, Dr Denny said the data for 2020-21 revealed a dramatic change in the age profile of people moving to Tasmania and those leaving, compared with the pre-pandemic period.

"If this interstate migration age profile continues, it is likely to have serious implications for economic production and demographic reproduction for Tasmania," she wrote.

"Considerably higher numbers of Tasmanians aged 25-39 left the state during financial year 2021, compared with the pre-pandemic average.

"For arrivals, considerably fewer people moved to Tasmania in the age groups 0-29, compared with the pre-pandemic average.

"Compared with pre-pandemic levels, interstate departures increased substantially for all age groups 25-39, ranging from an increase of 43.1 per cent for those aged 30-34 to 20.8 per cent for those aged 25-29.

"Compared with pre-pandemic levels, interstate arrivals declined for all age groups 0-29 ...

"These age profile movements will likely contribute to Tasmania's rate of population ageing increasing considerably, particularly given that overseas migration - which historically placed downward pressure on our median age - has also reversed to negative net figures."

Dr Denny said it was hard to predict if the age profile pattern would continue

'While this age profile data is for the financial year 2021 period only, interstate migration for the September 2021 quarter showed a further significant increase in net interstate migration loss, led by a 40 per cent increase in interstate departures compared with the previous year," she said.

She said further exploration of the reasons for Tasmanians leaving the state was warranted.

"While a government spokesperson may suggest that this significant shift in the interstate migration age profile is the result of the pandemic and could not be foreseen, I suggest that this trend had begun prior to the pandemic and that it is the repercussion from failing to plan appropriately for the population growth that preceded the pandemic, but was potentially exacerbated by the pandemic," she said.

" As such, the Tasmanian government's Population Growth Strategy requires an urgent review."

The strategy involves growing state population to 650,000 by 2050.

The ABS' estimate for September was 540,839.