The Ngái population was 4,841 in 1999 but down only 1,035 in 2009 and up to 1,649 in 2019.
In the years from 1999 to 2019, the Ngái population fluctuated: it was at 4,841 in 1999, decreased to 1,035 by 2009, and then rose to 1,649 in 2019.