Kids and Costs: A Guest Post on Twins by Bryan Caplan

Bryan Caplan, a professor of economics at George Mason University and a blogger for EconLog, is the author of a new book called “Selfish Reasons to Have More Kids: Why Being a Great Parent Is Less Work and More Fun Than You Think.”  He’s guest-blogging for us about parenting.  You’ll  be hearing more from Caplan in these environs soon, as he’ll be one of the guests in an upcoming Freakonomics Radio show tentatively titled “An Economist’s Guide to Parenting.”

Kids and Costs
By Bryan Caplan

One day when my wife and I were strolling our twin infants, we overheard a passing jogger tell her friend, “Now there’s a reason to shoot yourself.” Econ 101 suggests that she had a point. Economists usually assume that doubling output more than doubles costs; or as textbooks say, there are increasing marginal costs. So economists naturally expect twins to be more than double the effort, stress, and out-of-pocket cost of a singleton. As Joshua Gans of Parentonomics writes: “But regardless of the level of the cost curve for parenting, it is surely the case that the marginal costs of parenting for each additional child are increasing.”

Econ 101 was brutally accurate for the first three months of our twins’ lives. I was in charge of midnight feedings, and repeatedly faced an ugly dilemma: What do you do if one twin wakes up for food while you’re feeding his brother? Either way, you have a baby in tears.  But as our twins grew up, Econ 101 gradually drifted away from the facts, for three main reasons.

First, after infancy, most of the cost of parenting is fixed. People with one child live very different lives than people with zero children: Parents move to the suburbs, rarely travel, and stay home Saturday nights. But once you make these sacrifices, an extra child has little additional effect on your lifestyle. Maybe that’s why almost all of the negative effect of kids on parental happiness in the General Social Survey comes from kid No. 1.

Second, doubling your kids definitely less than doubles the financial cost of raising them. Hand-me-downs and nannies are the most obvious examples. But the deeper reason is that parents learn by doing. Once you discover the Ferber method for making babies sleep through the night, you can use it over and over.

Photo: iStockphoto

Third, as long as your kids play well together, more kids can actually be less work. Now that they’re eight, I’m convinced that our two twins demand less attention than one singleton. Why? Because each twin has a built-in playmate. We don’t have to entertain them much because they entertain each other.

Ultimately, Econ 101 does have the last word: If you keep having kids, you’ll eventually reach the point of increasing marginal costs. That’s good to know. But it’s at least as important to realize that your second, third, or fourth kid won’t cost as much as your first — and might even make your life easier.


I'm a twin and definitely appreciate this article.

One cost you didn't mention that you might want to consider - education. It seems like your article only applies to children before they reach their schooling years.

Any parents paying for private primary schools and college might disagree with your position.

lemmy caution

this is a good point.


My mother in law had undiagnosed identical twins. There was little ultrasound in 1982 Ireland. After the first was born the midwife asked her if "she wanted the good news or the bad news" the second twin was both.


The statement that Economists usually assume more than double costs for double output seems suspect. I can think of many instances where start up costs associated with an activity (such as construction) make the first increment substantially more expensive than the second, third, fourth...


The argument is that *at some point* along the costs curve you will reach a point where marginal costs are increasing. Before that point, marginal costs can decrease as returns to scale are realized. By arguing that usually doubling production more than doubling costs, economists assume that decreasing marginal costs have been taken advantage of - if the additional cost of building a second house at the same time as the first is lower than building two houses sequentially, a construction company will generally build two at the same time. But even if the second house is cheaper, it does not mean that building a third, fourth, etc will be cheaper; by doubling output from two to four at the same time, the construction company *may* more than double costs and at some point doubling production again *must* lead to a more than doubling of costs.


I agree, with Nate: as kids grow up the variable costs tend to increase compared to variable costs: education, entertainment, sports, etc. Even house size, especially if you start from a small apartment. Especially if you have opposite gender siblings.
Also time is not a fixed cost, especially for dual-earner families: it will be not all that common that siblings will get sick at the same time or do all the same activities, hence parents will have to take more time to accomodate for the extra child(ren)


I had (undiagnosed) fraternal twins in 1982. For one thing after 6 onths they were never the same size so what I bought in the larger size eventually fit the smaller of the two. Also I bought better stuff for my older kids since there was good use for it. In terms of effort, having kids who can play together is definitely an advantage in terms of keeping them busy say on trips. I don't think there is much advantage though in saving costs on feeding them or education. But, if that is your reason for or against having kids you should wait till you have a better reason.

VB in NV

Perhaps the jogger's comment was directed at your wife's plight of being married to an economist.


I wish freakonomics had a like feature.

Eric M. Jones

And each First-World child has a million kilogram CO2 footprint.


So why have you not killed yourself yet, since obviously you think we would be better off saving the CO2?


The elephant in the room here is education - basically, the thesis is premised upon the state paying for education via general taxation.

Here in the UK, for counter-example, the cost of a good (ie. private) education so dwarfs ANYTHING else, that the marginal costs of additional children are... well... I can't put an exact figure on it, but I'd say it is a LOT closer to 100% than it is to 50%!


Just what the world needs, more children.

We'd all be a lot better off if everyone kept to one or zero children per family.


More children of smart, productive people is EXACTLY what the world needs. Each such child is an enormous net benefit to society.

I must say, that as a mom to 2 sets of identical (surprise!) twins, there are some truths here, and some fallacies - depending on what exact 'economic' impact you are considering, as there are several that have come up: financial impact, parental effort and now, Carbon impact.

1 - financial impact. Yes, doubling production would definitely increase marginal costs in a facility that is already operating at capacity. However, most American homes and families do not have their 'capital' or fixed costs operating anywhere NEAR maximum capacity. How many empty seats are there in your car on your average drive? How many empty rooms in your house that could be used as bedrooms (or add a bunk bed or two? Even employer-sponsored health insurance often has only 2 coverage options: single or family - whether you have 1 child or 10, your premium remains constant. That said, until you have to buy a bigger car or add on to your home which are some major costs, you probably have economies of scale to take advantage of! The variable costs will be additional, but generally buying in bulk is cheaper: again, decreasing marginal costs.

On education - it depends on what your standards are for educating your children. If primary education is sufficient and you have access to a public school. Well, no increasing costs there. If you consider secondary education a necessity, different story. I think with the increasing costs of higher education compared to wages in this country that it will unfortunately become less common for the general population to have degrees. My personal view as a parent is that we will save as much as we can to help out, but ultimately our kids will go based on their own determination and necessity for their desired career and we'll help as much as we can and just hope that they are happy enough we got them that far!

2 - Parenting Effort: As mentioned in the article, there are definitely decreasing marginal costs associated with parental effort. But I want to dispel the myth that even two babies are more work than one. two colicky, non-sleeping babies who refuse a bottle in favor of breast definitely require more parental effort than 2 angel-sleep-all-day-feed-every-3-hours babies. This from my own experience. And according to other mothers of multiples I know that also had a singleton - even 1 cranky baby is more work than two 'easy' babies.

3 - Carbon Footprint: Each additional child has a much smaller carbon footprint than the first. Let's face it, buying in bulk saves on packaging. We drive together, play fewer video games because we are too busy doing other activities together, and have the heat going in only one home to keep us all warm, not to mention that the lights are only on in1 room when we are together. The additional costs of food and gas on a families' income also encourage creative ways to consume less - economic pressure that does not exist for a 1-child double income family that is too busy planning their Disney vacation to grow their own fruits and vegetables in their yard. I would go so far to say that those of you who are concerned about saving carbon impact on the world should just forgo children all together and let the rest of us take care of it for you - it will be MUCH, MUCH better for the environment! In fact if you'd like to send me a check to support this cause, I'll set up a 501(c) you can even make it tax deductible!


Ericka F.

Being a mother of twins (boy/girl) who are now 2, that the comments of "oh my gosh, I couldn't imagine, no way I could do it" are just words people say when they have nothing else to. The cost of childcare, education and everyday life is a challenge... but if you plan and have a great spouse/partner etc. then it "can work". Like someone stated in a post, that time is not a fixed cost and I can't agree more. Also the comment made in the article about having multiples vs. singleton's is completely correct!!! They constantly have someone to play with and on those rainy days (which are common right now in WA) they can entertain each other and they have a great relationship... as they got older, hanging around mom and dad got boring for them I guess :). I don't remember much of the first year...b/c it FLEW BY, but I guess that's the joy of twins!!!


I have 14 months old triplets. Initial costs of pram, car and cots is expensive, though marginal costs are lower as everything is bought in bulk and not wasted. Once they start sleeping through the night and are on a good routine, having the three interact is priceless. I live in Australia so health and education costs are relatively free. As triplets sharing becomes ingrained so the costs are far less then having three fully clothed singletons with a room full of their toys.

Al in all I am looking forward to saving money in the 'kids under five eat for free' restaurants


i understand the essential point that the author is making is "don't sweat having more kids because you have less of an effect on your kids than you think and each additional child requires less effort from you". sure, as long as kids require essentially identical care to meet their needs. but what about kids who have very different needs- whether they're cognitively limited, emotionally disordered, chronically medically ill, or have very different personalities? i'm guessing that the increase in efficient parenting that is the crux of the author's premise is present (if at all) to a much lesser extent.