"population drain" is correct and usable in written English.
You can use it to refer to a situation in which large numbers of people leave a particular area or country. For example: "The rapid population drain from rural areas is having a significant impact on the availability of services in these regions."
A previous article discussed the population drain in Buffalo.
Orr's plan addresses a core problem in Detroit: systemic population drain.
Bryan's tax base is eroding from the loss of manufacturing and a population drain.
The accompanying news articles are using phrases like "population drain" and "fleeing the state in droves".
The city is already smarting from a population drain, and the Buffalo area has one of the highest unemployment rates among major metropolitan regions in the country.
And because of the magnitude of Detroit's population drain, Michigan is the only state to register a net population loss since 2000.
The muffling or outright sequestration of half the population drains the variety and vibrancy from public life, makes men less interesting and sometimes less sensitive, removes from the visible scene and the field of journalism one of the crucial aspects of human life.
Walker and Segal found that 210 patients out of a total of 24,000 surgical admissions presented with acute appendicitis at CHBAH, while Murchison Hospital, in Southern Kwazulu Natal, reported only seven cases of acute appendicitis out of 8,000 admissions, with a potential population draining of 200,000 people to this particular hospital[9].
Sometimes, It remains patent as an isolated malformation, persistent left SVC (in 0.3% of the normal population) draining into the coronary sinus, which has an enlarged ostium.
Killings, rape, burnings Testimony gathered by human rights groups and The Hague tribunal, which has teamed up with the OSCE, the British military and the US Bar Association, points overwhelmingly to a well-coordinated scorched earth campaign aimed at displacing the ethnic Albanian population to drain the 'sea' in which the Kosovo Liberation Army guerrillas 'swim'swim
The vast tundra region, inhabited by a dispersed Inuit population and drained by the Thelon, is served by the trading posts of Baker Lake (Qamanittuaq; known for its Inuit tapestry) and Chesterfield Inlet (Igluligaarjuk).
