Last week, the populist Party for Freedom (PVV) asked questions in parliament about the costs and benefits of "allochtonen" [first and second generation immigrants, see insert] for the Dutch treasury: what do they cost the government and what tax revenue do they contribute? These questions are superfluous however.

It is clear that certain groups of immigrants are responsible for significant costs and that they generate little tax revenue in return. That is also true however for young people (aged 18 to 24, for example) and for people older than 65. Finally, this also concerns all other groups who make use of social security (about 25 percent of the working population, 1.6 million people).

With respect to the elderly, we could claim that they have contributed to the growth of our economy and that they are therefore entitled to reap the benefits. But in the PVV analysis that would only apply to those elderly who did in fact participate in the labour process and who paid taxes – not therefore all the women who put their time and energy into raising their families.

For young people, we could argue that the money spent on them is an investment in the future. We contribute to their education and in doing so enable them to provide for their (and our) future. I don't know what the PVV would do with regard to the remaining 1.6 million people who are clearly a net expense for the treasury because they receive benefits, since only a small percentage of this group are immigrants.

The energy that we would put into answering the superfluous question of what costs exactly are incurred for certain groups of immigrants could better be spent on solving the problems that have arisen. We must realise that it is impossible to chart out all the costs and certainly all the benefits. That is because many of the benefits – and some of the costs – lie in the future. This is also the argument we use with regard to young people.

But another reason is that the costs and benefits are interrelated, think for example of the old Dutch saying 'De kost gaat voor de baat uit' [roughly equivalent to the English saying: 'Nothing ventured, nothing gained']. In our ageing society we must accept all helping hands. The right question is how we can achieve the most benefits possible by investing in that.

At the moment, for each person over the age of 65, there are about five people of working age (18 - 65 years), who could in principle work. This ratio will have halved in twenty years' time: in 2030 there will be only 2.5 people of working age per pensioner. We clearly need new workers in order to produce enough income and care to compensate for our ageing population. By investing in assisting as many unemployed people as possible to find work, with special attention to newcomers and immigrants without jobs, we will enable them to guarantee their and our future.

It is not good policy to only pay out (increasingly lower) benefits as compensation for our failure to offer the unemployed and newcomers worthwhile employment. The challenge is to seek sensible ways, in a respectful manner, to help them build up a rewarding existence here. There are various examples of neighbourhoods and municipalities where this is happening successfully. Hopefully with its tendentious question the PVV will inspire society to in fact better face this challenge.