By Gavin Stamp
BBC News business reporter
A year on from the enlargement of the European Union, a clear picture has yet to emerge of the impact that it has had on migration in Europe.
Many migrants find themselves working in agriculture
Many of EU's original 15 member states including Germany, France and Italy still have tough limits on economic migration from the ten countries which joined the Union last May.
Transitional arrangements included in the accession treaty allowed the EU's existing 15 members to apply their own national migration legislation until at least 2006.
This gave them the right to impose entry quotas on workers in certain professions.
In contrast, the United Kingdom, Ireland and Sweden moved quickly to remove barriers in their labour markets under certain conditions.
UK government figures show that about 130,000 nationals from eight of the new member states - different rules apply for Cyprus and Malta as Commonwealth members - applied to work in the UK between May and December 2004.
About 123,000 successfully obtained work permits.
According to Home Office estimates, the new workers - over half of whom have found permanent employment - pumped about £240m into the British economy during that time.
Fears that migrant workers would act as a drain on the economy appear unfounded. More than 95% of incomers are working full time while the number drawing state benefits, according to the Home Office, are "very low".
About 75,000 people from the new member states are believed to be working in Ireland, according to government figures, while 4,000 have ended up in Sweden. No official figures are currently available for the other 12 EU countries.
"The general opinion is that this migration has been beneficial," says Dr Martin Ruhs, from the Centre on Migration, Policy and Society at the University of Oxford, who has studied the impact of the inflow of workers into Ireland.
"It continues to meet a need in terms of filling labour shortages and there have been no adverse effects such as a rise in unemployment levels."
Critics argue that some of Europe's largest economies, struggling with high unemployment and overburdened welfare systems, will have their problems exacerbated by a flood of migrants competing for jobs.
What evidence there is suggests that far from a mass exodus from east to west, numbers are likely to be limited.
About 40% of migrants now believed to be working in the UK were already living there before last May.
The European Foundation for the Improvement of Living and Working Conditions, a think tank established and funded by the European Union, estimates that about 220,000 workers a year will travel from east to west in search of employment by the end of the decade.
This would amount to about 1% of their combined populations.
Polish workers accounted for over half of economic migrants to the UK last year from the new EU states, and a third of migrants to Ireland.
Dr Hubert Krieger, from the European Foundation, says this is as much a reflection of Poland's size as it is of its struggling economy, where unemployment is 18%.
"The propensity to migrate is no higher in Poland than it is in any of the other nine countries," he says.
"Poland has a history of migration and substantial emigrant networks exist."
The lure of significantly better pay and job prospects will inevitably continue to attract workers from the fledgling market economies of eastern Europe and the Baltic states to Europe's biggest countries.
However, while the numbers are currently small, the danger to these countries' economic development is all too apparent.
The majority of migrants are aged under 34. Research suggests many are university educated, prompting real fears of a 'brain drain'.
While many seek seasonal short-term employment in the services, construction and manufacturing sectors with a view to eventually returning home, there are professionals - including teachers, doctors and accountants - who may be lost to their home countries forever.
"It is a problem, although we will have to see how many of these people return home quickly," says Dr Krieger.
"In relative terms the economic development prospects of these countries are very good, particularly in comparison to countries like Germany which have been doing very badly."
"I think there will be a substantial amount of return migration."
Experts believe that future migration levels will hinge on how quickly countries such as Germany open up their labour markets.
This is likely to depend on Germany's own economic performance which, in turn, relies heavily on the strength of the global economy.
"The benefits of migration are likely to be felt as long as there is continuing economic growth," argues Dr Ruhs.
"What happens if the US economy takes a downturn and there is a ripple effect and the Irish and UK economies continue to slow down, that is a different question."