One figure, say economists, is getting more difficult, not less, to predict for an economy that has gone to bust from boom: how many people will lose their jobs in this recession.

Forecasts by the government in the budget that unemployment would average 7.3% in 2009 have not been borne out. The November jobless rate reached 7.8% and will, all economists predict, keep on climbing.

The Economic and Social Research Institute (ESRI) will later this week revise its forecast for unemployment in 2009 sharply higher, and many economists now believe the jobless rate will not peak until 2011.

But matters could still become a good deal worse. Alan Ahearne of NUI Galway, who correctly predicted that Ireland faced a deep economic downturn some time ago, believes unemployment could peak at 10% or rise as high as 15%. That is a huge range, he said, because no one knows whether the international economy will bottom out by the middle of next year, and for Ireland, the big uncertainty remains how many recent migrants will stay in the country.

If the jobless rate were to reach 15%, then an already ballooning government deficit become an enormous deficit: the economic crisis here would look a lot like the bombshell that rocked Finland, a country of about 5.2 million people, in 1990. Its painful road to recovery is now being closely studied for lessons that Ireland and other former high-growth European countries may follow. Significantly, Finnish unemployment never again fell to 3.2%, the rate reached in 1990 before the bust.

"Predicting what happens to unemployment has become more difficult this time," said the ESRI's Alan Barrett. "Ireland once had sophisticated economic models of comparative wages between the UK that could predict flows. But we are in uncharted waters. We did not have good figures on migrants until recent times and things have deteriorated rapidly."

The Central Statistics Office estimated that 18.6% of the 268,586 people on the live register last month were so-called non-nationals. But CSO figures show that just under 10% of those registered were from the 12 EU accession states, while 4.6% were categorised as being from the UK, (which includes people born in the North); 3% were classified as "other nationals" and 1% were from the 13 EU states, excluding Ireland and Britain.

The figures suggest that there are fewer people on the live register from the recent accession states than many believe, and that the register includes other people, who are wrongly classified as "non-nationals". Many therefore are unlikely to leave the live register.

Dermot O'Leary, chief economist at Goodbody Stockbrokers, forecast that the jobless rate will peak at 11% in 2010, as 80,000 more construction industry workers lose their jobs. At the end of 2010, 120,000 construction workers will have lost their jobs from an industry which at its peak employed 290,000, he said.

Nonetheless, the path to recovery, said Pat McArdle, chief economist at Ulster Bank, who forecast the jobless rate will peak at between 10% and 12%, could be rapid once the economy starts growing again.