Sir

Older people commonly complain that they do not enjoy the respect of younger generations. The complaint is the more bitter because they feel they would have been respected in old age had they been born a century earlier. In the absence of any data from the eighteenth and nineteenth centuries to test the validity of this complaint, I decided to analyse the age at which British prime ministers and US presidents first took office. I reasoned that, by and large, voters would elect a leader from an age group they respected.

The results (Fig. 1) reveal a striking contrast between the two countries. British prime ministers became progressively older through the eighteenth and nineteenth centuries. In the twentieth century this trend is reversed. In the United States, there is no significant pattern. There were several quite old presidents at the outset, as four Founding Fathers took turns in the job. In the twentieth century, there have been some notably old presidents (Ronald Reagan and George Bush) and some notably young ones (John F. Kennedy and Bill Clinton).

Figure 1: The age at which British prime ministers and US presidents first came to power plotted against the year in which they assumed office.
figure 1

The US data show no significant trend but the British pattern is highly significant (P < 0.001), and the line shows the fitted second order polynomial.

Full size image

The British changes could have some connection with changes in the demographic profile of voters. Increases in life expectancy will make voters older on average while extensions in the franchise may have the reverse effect. The former is likely to be the stronger effect. However, I wish to offer an alternative perspective.

Biologists commonly argue that contests for mates and/or resources are often resolved by honest signals of quality1. Since such signals are costly to display, they cannot be displayed by low-quality cheats and therefore they reliably signal the high quality of the signaller. Could such arguments apply to the British data?

Two hundred years ago, the ability to survive beyond 50 indicated a genetic constitution able to cope with an environment where disease was widespread. Only in this century did life expectancy advance beyond 50 in developed countries2. Today, UK life expectancy is over 70, and survival to that age has ceased to indicate anything much about genetic constitution.

In Victorian times, prime ministers were drawn from the élite of society and proved their ability to operate in that stable milieu. In today's more rapidly changing society, there is a case to be made that the ideal prime minister is one who has risen to prominence quickly because he or she shows the necessary flexibility to lead the nation in a time of transformation.

I suggest that British voters give the top job to somebody whose attributes are honest signals of ability in the society of the day. Prime ministers became older as life expectancy increased. But the pattern reversed this century when voters realized that an elderly member of the élite was no longer a likely possessor of useful physical or social qualities. At a less elevated level, this may sadly mean that today's older people are correct to grumble about lack of respect. What is less evident is why US voters are not following the British pattern.