Marchetti’s constant

by Lorenzo Piccoli


In Italy, according to the most recent data before the start of the Covid-19 pandemic, 22 million people moved every day to go to work and one in two workers spent more than thirty minutes on public transport. In the US, the average worker spent 225 hours (over nine calendar days per year) commuting. For many of these people, commuting to and from work can be the worst part of the day. For others, commuting is an important ritual that helps to keep a balance, decompress and disengage.

However, since the pandemic started, a lot of these people are working from home (and working 3 hours more daily than they did before). What happens when you do not commute to work?

I have read a series of articles on this topic (in Italian, in English). I have a personal interest at stake. Boundaries between my work and my home have completely collapsed since the start of the pandemic. I am constantly exposed to emails, online meetings, calls. I feel like a Netflix show: always available, on demand. A large body of research over the past four decades shows that a certain degree of psychological distance is essential to live well.

One strategy to cope is to do fake commuting: start and finish the day with walks, runs, bike rides, or whatever gives you pleasure. In Paris, between November and December, I used to wake up and run, and I would disconnect in the evening and drink a beer with Arianna. It helps, but it is nearly as effective as traditional forms of commuting.

The Wall Street Journal tells the story of an editor of a New York music magazine who was accustomed to reading books on the subway every day on his way to work. Taking an hour each morning to do the same thing at home didn’t work out much. He attributes the ineffectiveness of this alternative practice to the fact that he is somehow more available on the phone than he was on the subway. ‘There are books that I started reading during the pandemic and I haven’t been able to finish, and that didn’t happen before‘.

This is a sudden bankruptcy of our ‘travel time budget’, what in 1974 an Israeli engineer under the nae of Yacov Zahavi called ‘a stable daily amount of time that people make available for travel‘. In 1994 an Italian physicist, Cesare Marchetti, picked this idea up and wrote a paper, Anthropological Invariants in Travel Behaviour, on the ‘quintessential unity of travelling instincts around the world, above culture, race and religion‘. Marchetti explained that humans had always been willing to spend about about 30 minutes a day travelling from and to home: for hunting and gathering, farming, going to the office…

The idea of a standard commuting time being 30 minutes each way has become known as Marchetti’s Constant.

The intuition is that forms of urban planning and transport change over time, but people gradually adjust their lives to their conditions such that the average travel time stays approximately constant.

That is, of course, until a pandemic strikes.