From a New York Times article dated 9 January 2007 -
"In Geneva, the office of the United Nations High Commissioner for Refugees announced an emergency appeal today for what it said were an estimated 3.7 million Iraqis who had been displaced internally or had fled abroad as a result of the fighting.
The agency said that about 1 in 8 Iraqis had left their homes, in what it called “the largest population movement in the Middle East since Palestinians were displaced following the creation of the state of Israel in 1948.”
“There is currently no end in sight” to the Iraqi exodus, the agency’s statement said.
John O’Neil contributed reporting from New York."
Since the Palestine Mandate had 1.8 million total population in 1948 this is about what one expects from the UN and from the NYT.