More Sex is Safer Sex and Other Surprises

More Sex is Safer Sex and Other Surprises


An article by Professor Steven E. Landsburg, University of Rochester, New York

Would the world be a better place if sexually cautious people went out and got more partners? Apply economic logic to the question and you may get a result that deviates far from common sense says Professor Steven E. Landsburg at the recent Warwick Economic Summit 2012. It’s all down to the costs and benefits.
We all learnt in childhood that you can have too much of a good thing. We know we should have dinner tonight but are not sure if we should reach for that third helping. We know our town should have a fire department but should it have a bigger fire station? That’s something we don’t know. “So the interesting economic problem is, how do you know when you’ve had enough?” asks Prof Landsburg.
Here’s where economic logic comes in. “Logic is both fun and useful, and economic logic in particular sometimes surprises you,” he says. “Just as you can have too much of a good thing, you can have too little of a bad thing – take pollution for example.” There’s universal agreement that pollution is a bad thing yet nobody would want to live in a world with zero pollution because that would mean we would be without buildings and travel. Pollution, says Prof Landsburg, is a necessary by-product of other things that we like having so we put up with a certain amount.
“That raises the interesting question, do we currently have too much pollution or too little? Once you’ve agreed that the right amount is not zero, it’s not immediately obvious whether we would be happier in a world with more or with less.”
His answer is that the world has too much pollution and we’d be happier with less. “And here’s why I say that: because by and large, the people who decide to create pollution are not the people who have to live with the consequences of that pollution.” When people don’t have to live with the consequences of their actions there’s little incentive to reign in the bad behaviour and concentrate on the good. “That’s why we have too much pollution and too few people out in the park picking up trash.”
Prof Steven E. LandsburgWhat if we take that principle and apply it to the question of whether the world has too much or too little casual sex? “Suppose for starters that you happen to be a very reckless, promiscuous person with a lot of partners in the past. You go out tonight looking for a new partner... you’re making the world a more dangerous place for other people and you’re doing that in a way where the costs largely fall on other people rather than on you. You’re polluting the partner pool that everybody else is fishing in.” These promiscuous people are more likely to spread diseases, says Prof Landsburg, and when they choose to take another partner they don’t fully account for the costs they’re imposing on the rest of the world.
Yet look at the flip side. “Suppose instead that you are a particularly cautious person, a person who is statistically much less likely than the average person to be infected with anything terrible. You go out tonight and you take a new partner, you’ve made the world a safer place. That person who is going home with you is having safer sex than they realise. You have improved the quality of the partner pool.”
Using the costs and benefits test Prof Landsburg works out that the cautious person is not having enough partners because a lot of the benefit of their behaviour is falling on other people. The cautious person isn’t accounting for that when they’re deciding how many partners to have. “I suggest the world would be a better place if we could get those very cautious people to go out and have more partners. Not too many... because we don’t want to turn them into those promiscuous dangerous people... as with everything else there’s a right amount.”

Logic is both fun and useful, and economic logic in particular sometimes surprises.
Therefore pure economic theory tells Prof Landsburg that the world would be a better place and social gain/social welfare would rise if the very promiscuous people reigned themselves in and if the very cautious people loosened up a little bit. But what does an economic welfare rise mean? There are, according to Prof Landsburg, two different ways it could happen in this context.
The first is that the spread of disease could be actually slowed down. The second is that there may be some increase in the amount of disease, but there would be such a disproportionately large increase in that amount of sexual activity that welfare would go up: “because people were having so much fun that it compensates for the additional diseases spread”.
“Pure theory tells us that when people don’t take account of all the benefits that they are imposing on other people then if you could get them to do a little more of this stuff, welfare would go up.” The theory, however, doesn’t tell you how welfare would go up – that takes more theory.
Michael Kremer at Harvard University used epidemiology and modelling to answer this question. He says that if cautious people had more sex then welfare would increase. Kremer’s estimate is that if you took everybody in Great Britain who currently averages fewer than two and a quarter partners a year, and brought them all up to the two and a quarter partners per year level, then you would substantially slow down the speed of HIV.
That’s a surprising conclusion and one that seems to go against common sense. Don’t worry about that, closes Prof Landsburg. “Common sense is what tells you the earth is flat”.

Steven E. Landsburg is Professor of Economics at the University of Rochester, New York. He is author of The Armchair Economist and writes a column for Slate magazine about topics ranging from the national debt problem to the obesity crisis.
His research topics are varied, such as using the language of microeconomics to explain and justify the everyday decisions that we make and the social and economic patterns that result. Prof Landsburg’s more recent work include the (career) cost of motherhood and whether or not daughters (as opposed to sons) cause divorce.
Photograph by Felix Li, Warwick Photosoc.

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