The labour force will continue to increase by as much as 28,000 people a year at least until 2011, according to the latest research from the Central Statistics Office.

As a result of continued net immigration, the CSO has estimated that the labour force will reach almost two million by 2011 from 1.62 million in 1998.

The continued increase will underline continued growth in the economy.

At the same time, in its latest Population and Labour Force projections, the CSO has estimated that the female share of the labour force will continue to increase, reaching 43 per cent by 2011.

Underlining the need for the State's recent pension initiative, the CSO has also found that the population aged over 65 will double between 1996 and 2031 no matter what assumptions are made about levels of migrations.

The numbers in this age group will be around 850,000 in 2031, compared with the 1996 level of 414,000. "We will then officially be old country," said Mr Aidan Punch of the CSO.

The numbers of very old are also set to rise dramatically with the consequent demands on health care.

The CSO predicts that the numbers of those aged 80 or over will rise to more than 200,000 in 2031 from the 1996 level of 90,000.

As a result, the so-called demographic dividend which has helped boost growth in recent years will last only until 2006. After that period the numbers of old people who need to be supported will start to be felt.

At the same time the population is expected to reach four million by 2006, for the first time since the 1870s.

By 2011, the population is expected to be in a range of 44.3 million, depending on the extent to which migration continues.

In the longer term, the population may reach 4.8 million, which would be the highest since the 1850s.

The CSO also found that in the very short term - or until 2001 - births are set to rise.

However, in the long term births will decline due to an expected fall in the number of women between the ages of 20 and 39.

As a result, the number of children of primary school age is expected to pick up after a recent decline and is likely to be within 5 per cent of the 1997 level by 2011.

After this, births are expected to decline and the 0 to 14 age group will fall by about a third over the longer term.

The outlook for secondary school pupils is more certain and numbers are expected to decline by just more than 20 per cent in the 15-year period to 2011.

The CSO used a number of assumptions when making these projections.

It has assumed that male life expectancy will rise to 77.8 in 2031 from 73 and that female life expectancy will rise to 84 from 78.7.

The most difficult variable is, of course, the level of migration and CSO officials warned that they had often had to revise these quite dramatically in the past.

On one assumption they assumed migration would continue until 2006 before tapering off and eventually returning to slight emigration, while the more bullish assumption is that migration will continue, albeit on a declining scale, until 2031.