Brussels - Of the more than 500 million people in the European Union, about 34 million or less than seven percent are counted as migrants.

Of that total, 14.3 million are EU citizens who have taken advantage of the bloc's free movement possibilities, while just under 20 million come from third countries outside.

Here is a breakdown of Europe's migrant numbers:

Smaller countries

Some of the smaller EU countries, led by one of the smallest of all, Luxembourg, have opened their doors widest in proportion to their demographic size.

More than 45 percent of the population of Luxembourg are foreigners, attracted by its high standard of living, according to the EU's statistical agency, Eurostat.

Cyprus follows on 19.5 percent, Latvia 15.2 percent, Estonia 14.9 percent, Austria 12.5 percent, Ireland 11.8 percent and Belgium 11.3 percent.

In eastern Europe, however, Poland, Romania, Croatia, Lithuania are all at less than one percent.

Poland in turn is one of the largest sources of citizens living in other EU countries, ranking in the top five in 10 member states.

Short-term foreign workers

The number of short-term foreign workers in EU countries is surprisingly small despite a 60-percent increase from 2010 to about two million in 2015.

Sent by their employer to work in another member state, this category accounts for less than one percent of jobs in the EU, concentrated largely in construction and manufacturing.

Germany takes most of these foreign workers at more than 418,000 in 2015, followed by France on 177,000 and Belgium 156,000.

By origin, more than 250,000 come from Poland, with 218,000 from Germany and 130,000 from France.

Non-EU influx 

The EU experienced a massive influx of migrants from outside the bloc in 2015 and 2016, most of them fleeing war and upheaval in Syria and across the Middle East.

According to the International Organization for Migration (IOM), of the more than a million refugees making it to Europe in 2015, 850,000 crossed into Greece via the Aegean Sea.

More than half came from Syria and most of the rest from Afghanistan and Iraq.

The Aegean route has largely been closed down by a landmark March 2016 EU-Turkey accord but the overall numbers have not changed much, with the central Mediterranean now the main route.

The EU considers most people using this route to be economic migrants, who will ultimately be returned to their home countries.

Economic impact

The European Commission, the EU's executive arm, concluded in a 2015 report that perhaps three million refugees would make it to the the bloc by 2017.

Their arrival would at least initially lead to increased public spending commitments in several member states, it said.

Giving an assessment of the economic impact, it said public expenditure can help to boost growth but may also hurt public finances if funded by loans.

"The report shows that the influx of refugees, if it is properly managed, will have (on balance) a small favourable impact on growth in the short and medium-term," the Commission said.