The great immigration debate has to become the great rethinking and restructuring debate.

Charlie Brown is right when he says “no problem is too big and complicated that it can’t be run away from”.

In both the US and the EU, the focus is increasingly on the problem of immigration.

President Donald Trump talks of them being criminals, drug traffickers and scroungers. And then he wants to build a very expensive wall on the border separating countries that for a long time have not countenanced war or terrorism against each other. (By the way, there is a funny Mexican joke: “Yes, it’s a good idea to build the wall — it will keep Trump out”!)

There are good reasons for allowing low-skilled immigrants in. (In this column I use the word “immigrants” to include refugees.)

Senior analyst and columnist Shikha Dalmia gave some good reasons why this should be so.

1. Americans are the customers of low-skilled immigrants, buying services from them, everything from hospital cleaning to childcare to repairs to the house.

2. These immigrants are mobile since they rent rather than own. So they can move to where the work is. Right now they are being encouraged to move to Detroit where much of the population has fled the city’s decay and the mayor is trying to revitalise it.

3. They are good for American and European women. Often nannies, they enable many women to work. Many of these are high skilled and therefore contribute a good deal to society.

4. Immigrants cost the state less than ordinary workers. They often fail to qualify for benefits. Of course, they cost the state when it comes to schooling or medical care, but then, they pay taxes (unless they are illegals).

5. They create jobs. They reduce the costs of production and make American or European goods more competitive with Latin American, Chinese, Indian and African exports.

Some economists argue that immigrants pull the wages of the host community down, but Dalmia says they have got it wrong. She says that it is a win-win situation, since immigration works to maximise the potential of the economy across the board. This lifts all boats.

6. As long ago as the 1960s, research work done in London made the point, supported by academic work today, that immigrants, apart from refugees, only journey to a country if they hear on the grape vine that lots of jobs are available. If not they do not come.

7. A 2005 World Bank report found that if the wealthier countries allowed a 3 per cent rise each year in the size of their labour forces through easier immigration, the gains to Third World countries over time would be about $300 billion.

Fully open borders would double the national income of the world in a few decades, virtually eliminating global poverty.

John Stuart Mill, the great 19th century economist, wrote that migration was “one of the primary sources of progress”.

Adam Smith also opposed restrictions on immigration.

Ironically, it was Karl Marx who seemed to be against immigration. He wrote that England’s decision to absorb the “surplus” Irishmen driven out by the famine was a ploy by the English bourgeoisie to “force down wages and lower the material and moral position of the English working class”.

But there are arguments for limiting the flow in the future.

If you fill an empty bottle with water, it is good stuff until it overflows. Then it no longer is useful to the drinker.

In my book “Conundrums of humanity: The big foreign policy questions of our day”, I argue that there are enough immigrants already (apart from refugees who should not be refused).

Those who readily argue for more are the middle and upper middle class who not only benefit from their jobs but enjoy the food and music that immigrants bring with them.

But it is the lower middle class and working class who often live cheek by jowl with immigrants. It is they who see their schools and health facilities become overcrowded.