Space census
http://www.neoscifi.com/SPACEPOP.html
For each year, it includes the highest number of people in space simultaneously during the year, and also the lowest number in space during the year. Sometimes it goes as high as 10 or more. The all-time high is 13 people in space simultaneously.
From the "Low" column, you can see that in fact space has had a human population continuously since 2001. During the years since then, the human population of space has never dipped lower than 2. So the period since 2001 really is the age of human habitation of space.