The Dutch government is in need of more prisoners.
There are now more guards and other staff than inmates in the Netherlands for the first time, according to data released by the Justice Ministry.
In 2008, there were more than 15,000 inmates, but by March this year there were 9,710, compared with 9,914 staff.
Crime rates have fallen slightly in recent years but are not notably lower in the Netherlands than in neighbouring countries, and many Dutch people think sentences for violent offenders are too light.
Justice Ministry spokesman Jochgem van Opstal said: "We're studying what the reason for the decline is."
A report in Britain last year, meanwhile, showed that close to a quarter of all prisoners in England and Wales were kept in overcrowded cells in the year to April.
The Howard League for Penal Reform said figures showed about 19,140 inmates on average were made to share a cell designed for one person.
It said overcrowding was "far worse than anyone imagined".
Figures published by the Ministry of Justice show that jails held an average of just over 85,000 prisoners between April 2012 and March 2013.