New European Union members

On January 1, Bulgaria and Romainia became the newest members of the European Union (EU), bringing the EU's population to 493 million.

From here.

The European Union has more people than the United States, Canada and Mexico combined. It has economic divides almost as stark as the NAFTA three. It does so with no internal limitations on immigration in the long term. There are some limits for a transitional period however:

Worried about the potential of being overwhelmed by workers moving from poorer, new Member States to richer old ones, the treaties governing the accession of new members have a "transitional" clause that allows existing Member States to restrict the free movement of "accession" workers for up to seven years.

This is the same provision that enabled 12 of the then-15 existing EU members (EU-15) to place limitations on workers from eight eastern European accession countries that joined the EU in 2004 (the A-8). There were no restrictions for nationals from Malta and the Greek-controlled portion of Cyprus, the two other countries that joined in 2004.

As in 2004, the majority of the EU-15 have placed short-term limitations on the number of new eastern European accession nationals they will allow into their labor markets. Of the EU-15 who chose restriction in 2004, only Finland has decided to allow free access in this round of enlargement. Sweden, which had a liberal regime in 2004, will again be open to labor migrants.

The UK and Ireland, which allowed free movement to A-8 workers, have announced restrictive measures.

Who is in the E.U. and when did they join?

1952–58 – Belgium, France, Italy, Luxembourg, West Germany*, Netherlands (*in 1990 reunified with former East Germany, Algeria was an integral part of France until 1962)
1973 – Denmark, Ireland, United Kingdom (*Greenland leaves 1985)
1981 – Greece
1986 – Portugal, Spain
1995 – Austria, Finland, Sweden
2004 – Czech Republic, Cyprus, Estonia, Hungary, Latvia, Lithuania, Malta, Poland, Slovakia, Slovenia
2007 – Bulgaria, Romania

The transition period for the 2004 entrants ends in 2011. The transition period for this year's entrants ends in 2018.