The percent of non-Western immigrants among the youth is still going up in the four big cities. Amsterdam has about 55% immigrant youth, and Rotterdam also has more than 50%.
About 33% of the total population in Amsterdam, Rotterdam and The Hague are non-Western immigrants. This has gone up by less than 1% a year in the past 10 years (~25% in 1996, ~30% in 2001). That is a much higher percent than the total over the country. The Netherlands has 11% non-Western immigrants (about 1.8 million out of 16.3 million).
While the percent of 1st generation immigrants is going down, the 2nd generation is growing. Many non-Western immigrants are in the age when they start families.
Non-Western is defined as immigrants from Turkey, Africa, Latin America and Asia (not including Indonesia and Japan).
Source: Elsevier (Dutch)
If this continues by this trend the major cities will have a majority of non-Western immigrants in 25 years. However, it is being offset by a move to the smaller cities. The Dutch Bureau for Statistics estimates that in 20 years the population in both big and medium size cities will stabilize at 30%.
See also: Netherlands in 2025