Dear Economist: How can I be fair to my grandchildren?

My son has two children and my daughter four. I propose to give £5,000 to each grandchild in my will. Would this be equitable, given that £20,000 would go to my daughter’s side of the family and only £10,000 to my son’s?
Mr Robinson

Dear Mr Robinson,

Let me be frank: at first glance I thought your dilemma was idiotic. If you want to hand out equal shares, that’s fine – but make your mind up. Given your daughter’s fecundity and some basic arithmetic it is quite clear that you cannot simultaneously give equal shares to grandchildren and to children.

Why, then, would you hand out £5,000 to each grandchild and still fret about fairness between your children? Your children don’t get the money; your grandchildren do. Similarly, it would make no sense to hand out £15,000 to each child and then start worrying that your grandchildren had been unequally treated.

Yet arch-rationalists such as Gary Becker or Robert Barro might leap to your defence. Assume your children are Becker-Barro altruists. This means that they care not about how much cash they give, but about the total sum their children receive from all sources.

If you give your grandchildren £5,000 each, that is simply £5,000 that their parents don’t have to give. They will adjust their bequests in the light of yours. Viewed in this way, your attempts to give money to your grandchildren are really hidden transfers to your children – and you would be quite right to worry that your daughter was getting more than your son.

But before you pat yourself on the back (Becker has a Nobel prize; Barro may get one too), ask yourself if your children are Becker-Barro altruists. Most people focus narrowly on their bequests, not on the total receipts of their offspring. I doubt your children are Becker-Barro altruists. After all, you aren’t.

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Tim, also known as the Undercover Economist, writes about the economics of everyday life.