Not the largest group of total immigrants from past years still in the country, just to be clear - that would take a long time - but the largest group
now coming. At least according to data just released
by the Pew Research Center; they aim to include both legal and illegal immigrants, and of course the latter must be estimated.
It's a little hard to know whether this is a temporary blip caused by the crash in certain lower-skilled sectors, but if it continues it would certainly affect the long-term demographics of the country in various ways.
One thing I find in general is that the media and the popular imagination tend to underestimate the share of immigrants who are coming through established legal channels, who are often well-educated.