How many Christian missionaries in the world?

I've heard two numbers: 400.000 and 700.000 both from fairly reliable sources. So my guess is there are between 4-700.000 career missionaries in the world today. This number does not count people that go on short term missions trips. There are not even a million out there for a world population of 6.6 billion people. Like the Lord said: The harvest is plentiful but the workers are few.