Shame you can't load the second link - it's mostly graphs and charts, so there's not much
Dutch there. What I can tell you is that 1497 living women have it as their first name right now, and 636 as (one of) their second name(s). That's 0.0202% and 0.0086% of the population (I don't know if that's female population or entire population). No men bear the name. It's very rare at this point in time, and even in 1880 (the records don't go further back) only 71 newborn girls were named Niesje (
http://www.meertens.knaw.nl/nvb/populariteit/absoluut/vrouw/afbeelding/naam/Niesje). Currently it's most popular from the city of Rotterdam up to the province Drenthe (
http://www.meertens.knaw.nl/nvb/verspreiding/absoluut/vrouw/afbeelding/naam/Niesje). For its etymology it directs back to
Agnes. I can't find any stats about Belgium, though.
Perhaps one did not want to be loved so much as to be understood -
George Orwell, 1984