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Viewing: Blog Posts Tagged with: ratio, Most Recent at Top [Help]
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1. Why are married men working so much?

By John Knowles


If you become wealthier tomorrow, say through winning the lottery, would you spend more or less working than you do now? Standard economic models predict you would work less. In fact a substantial segment of American society has indeed become wealthier over the last 40 years — married men. The reason is that wives’ earnings now make a much larger contribution to household income than in the past.  However married men do not work less now on average than they did in the 1970s.  This is intriguing because it suggests there is something important missing in economic explanations of  the rise in labor supply of married women over the same period.

One possibility is that what we are seeing here are the aggregate effects of bargaining between spouses. This is plausible because there was a substantial narrowing of the male-female wage gap over the period. The ratio of women’s to men’s average wages; starting from about 0.57 in the 1964-1974 period, rose rapidly to 0.78 in the early 1990s.  Even if we smooth out the fluctuations, the graph shows an average ratio of 0.75 in the 1990s, compared to 0.57 in the early 1970s.

The closing of the male-female wage gap suggests a relative improvement in the economic status of non-married women compared to non-married men. According to bargaining models of the household, we should expect to see a better deal for wives—control over a larger share of household resources – because they don’t need marriage as much as they used to. We should see that the share of household wealth spent on the wife increases relative to that spent on the husband.

Bargaining models of household behavior are rare in macroeconomics. Instead, the standard assumption is that households behave as if they were maximizing a fixed utility function. Known as the “unitary” model of the household, a basic implication is that when a good A becomes more expensive relative to another good B, the ratio of A to B that the household consumes should decline.  When women’s wages rose relative to men’s, that increased the cost of wives’ leisure relative to that of husbands. The ratio of husbands’ leisure time to that of wives should therefore have increased.

In the bargaining model there is an additional potential effect on leisure: as the share of wealth the household spends on the wife increases, it should spend more on the wife’s leisure. Therefore the ratio of husband’s to wife’s leisure could increase or decrease, depending on the responsiveness of the bargaining solution to changes in the relative status of the spouses as singles.

To measure the change in relative leisure requires data on unpaid work, such as time spent on grocery shopping and chores around the house.  The American Time-Use Survey is an important source for 2003 and later, and there also exist precursor surveys that can be used  for some earlier years. The main limitation of these surveys is that they sample individuals, not couples, so one cannot measure the leisure ratio of individual households.  Instead measurement consists of the average leisure of wives compared to that of husbands. The paper also shows the results of controlling for age and education. Overall, the message is clear; the relative leisure of married couples was essentially the same in 2003 as in 1975, about 1.05.

One can explain the stability of the leisure ratio through bargaining; the wife gets a higher share of the marriage’s resources when her wage increases, and this offsets the rise in the price of her leisure.  This raises a set of essentially  quantitative questions: Suppose that marital bargaining really did determine labor supply how big are the mistakes one would make in predicting labor supply by using a model without bargaining?  To provide answers, I design a mathematical  model of marriage and bargaining to resemble as closely as possible the ‘representative agent’ of canonical macro models.  I use the model to measure the impact on labor supply of  the closing of the gender wage gap, as well as other shocks, such as improvements to home -production technology.

People in the model use their share of household’s resources to buy themselves leisure and private consumption.  They also allocate time to unpaid labor at home to produce a public consumption good that both spouses can enjoy together.  We can therefore calibrate the  model to exactly match the average time-allocation patterns observed in American time-use data. The calibrated model can then be used to compare the effects of the economic shocks in the bargaining and unitary models.

The results show that the rising of women’s wages can generate simultaneously the observed increase in married women’s paid work and the relative stability of that of the husbands. Bargaining is critical however; the unitary model, if calibrated to match the 1970s generates far too much of an increase in the wife’s paid labor, and far too large a decline in that of the men; in both cases, the prediction error is on the order of 2-3 weekly hours, about 10% of per-capita labor supply. In terms of aggregate labor, the error is much smaller because these sex-specific errors largely offset each other.

The bottom line therefore is that if, as is often the case, the research question does not require us to distinguish between the labor of different household or spouse types, then it may be reasonable to ignore bargaining between spouses.  However if we need to understand the allocation of time across men and women, then models with bargaining have a lot to contribute.

John Knowles is a professor of economics at the University of Southampton. He was born in the UK and schooled in Canada, Spain and the Bahamas. After completing his PhD at the University of Rochester (NY, USA) in 1998, he taught at the University of Pennsylvania, and returned to the UK in 2008. His current research focuses on using mathematical models to analyze trends in marriage and unmarried birth rates in the US and Europe. He is the author of the paper ‘Why are Married Men Working So Much? An Aggregate Analysis of Intra-Household Bargaining and Labour Supply’, published in The Review of Economics Studies.

The Review of Economic Studies aims to encourage research in theoretical and applied economics, especially by young economists. It is widely recognised as one of the core top-five economics journals, with a reputation for publishing path-breaking papers, and is essential reading for economists.

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Image credit: Illustration by Mike Irtl. Do not reproduce without permission.

The post Why are married men working so much? appeared first on OUPblog.

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2. Thoughts of Pi

By Jason Rosenhouse


A recent satirical essay in the Huffington Post reports that congressional Republicans are trying to legislate the value of pi. Fearing that the complexity of modern geometry is hurting America’s performance on international measures of mathematical knowledge, they have decreed that from now on pi shall be equal to three. It is a sad commentary on American culture that you must read slowly and carefully to be certain the essay is just satire.

It has been wisely observed that reality is that which, when you stop believing in it, doesn’t go away. Scientists are especially aware of this, since it is sometimes their sad duty to inform people of truths they would prefer not to accept. Evolution cannot be made to go away by folding you arms and shaking your head, and the planet is warming precipitously regardless of what certain business interests claim to believe. Likewise, the value of pi is what it is, no matter what a legislative body might think.

That value, of course, is found by dividing the circumference of a circle by its diameter. Except that if you take an actual circular object and apply your measuring devices to it you will obtain only a crude approximation to pi. The actual value is an irrational number, meaning that it is a decimal that goes on forever without repeating itself. One of my middle school math teachers once told me that it is just crazy for a number to behave in such a fashion, and that is why it is said to be irrational. Since I rather liked that explanation, you can imagine my disappointment at learning it was not correct.

In this context, the word “irrational” really just means “not a ratio.” More specifically, it is not a ratio of two integers. You see, if you divide one integer by another there are only two things that can happen. Either the process ends or it goes on forever by repeating a pattern. For example, if you divide one by four you get .25, while if you divide one by three you get .3333… . That these are the only possibilities can be proved with some elementary number theory, but I shall spare you the details of how that is done. That aside, our conclusion is that since pi never ends and never repeats, it cannot be written as one integer divided by another.

Which might make you wonder how anyone evaluated pi in the first place. If the number is defined geometrically, but we cannot hope to measure real circles with sufficient accuracy, then why do we constantly hear about computers evaluating its first umpteen million digits? The answer is that we are not forced to define pi in terms of circles. The number arises in other contexts, notably trigonometry. By coupling certain facts about right triangles with techniques drawn from calculus, you can express pi as the sum of a certain infinite series. That is, you can find a never-ending list of numbers that gets smaller and smaller and smaller, with the property that the more of the numbers you sum the better your approximation to pi. Very cool stuff.

Of course, I’m sure we all know that pi is a little bit larger than three. This means that any circle is just over three times larger around than it is across. The failure of most people to be able to visualize this leads to a classic bar bet. Take any tall, thin, drinking glass, the kind with a long stem, and ask the person sitting nearest you if its height is greater than its circumference. When he answers that it is, bet him that he is wrong. Optically, most such glasses appear to be much taller than they are fat, but unless your specimen is very tall and very thin you will win the bet every time. The circumference is more than three times larger than the diameter at the top of the glass. A vessel so proportioned that this length is nonetheless smal

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3. Pythagoras & the Ratios

I'm very pleased to announce the release of my most recent book, Pythagoras and the Ratios from Charlesbridge Publishing. I posted a couple interior illustrations in a previous post - you can see them here. You can see another interior page if you visit this image viewer at Barnes & Noble and a couple more also at Amazon.com if you use the "Look Inside" feature.

If you have/know any kids learning or struggling with ratios then this is the book for them. Here's a description/review from the School Library Journal:

"Gr 4–7—This picture-book introduction to ratio and proportion also explains the connection between math and music through a story featuring young Pythagoras and his family. Preoccupied by mathematical problems, the protagonist is constantly in trouble with his parents for neglecting his chores. When his cousin Octavius offends everyone's ears with the dissonant pipes he is practicing for an upcoming music contest, the young mathematician hears a challenge. He measures his own set of melodious pipes, calculating the ratio of each pipe to the shortest one, and discovers that Octavius's pipes need to be shortened. Later, he tunes other cousins' lyres by attaching rocks to the strings to adjust the tension. With all the instruments finally ready, the cousins play together at the contest. Unfinished chores and a broken set of pipes leave Pythagoras out of the performance, but the end result is the first "rock" group, which is a big success. The story is amusing and offers a glimpse into life in ancient Greece. Acrylic and colored pencil cartoons depict the clothing and lifestyle of the period in a pleasing palette. A historical note and an experiment in which readers are challenged to use Pythagorean ratios to create a musical instrument with six glasses of water in varying amounts are appended.—Barbara Auerbach, PS 217, Brooklyn, NY"

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