America is becoming a more class-stratified society, contrary to the nation’s self-image as a socially dynamic meritocracy. In particular, the barriers are hardening between the upper middle class and the majority below them. As New York Times contributor Tom Edsall writes (“How the Other Fifth Lives"), “The self-segregation of a privileged fifth of the population is…creating a self-perpetuating class at the top, which is ever more difficult to break into.”

This separation of the upper middle class by income, wealth, occupation and neighborhood has created a social distance between those of us who have been prospering in recent decades, and those who are feeling left behind, angry and resentful, and more like to vote for To-Hell-With-Them-All populist politicians. As I told Charles Homans, also writing on class for the Times, “The upper middle class are surprised by the rise of Trump. The actual middle class is surprised we’re surprised.”

Edsall cited my earlier essay, “The Dangerous Separation of the American Upper Middle Class,” and quoted me as follows:

“The top fifth have been prospering while the majority lags behind. But the separation is not just economic. Gaps are growing on a whole range of dimensions, including family structure, education, lifestyle, and geography. Indeed, these dimensions of advantage appear to be clustering more tightly together, each thereby amplifying the effect of the other.”

Just as certain disadvantages can cluster together, creating multidimensional poverty, so advantages may cluster together, resulting in multidimensional advantage. Is there more clustering of advantages at the top of American society? Yes.

The top fifth of households by income obviously have more money than the 80 percent below them. What about other advantages? Let’s take just three: marriage, employment and education. (See Sean Reardon and Kendra Bischoff’s paper on the geographical segregation of affluence). You would expect people in top-quintile households to be more likely to have a graduate or professional degree; to have two earners in the family; and perhaps also to be married. You would be right.

The difference in the proportion of the top fifth with each of these other advantages compared to the bottom four-fifths is around 20 percentage points (we restrict our analysis to those aged 40-50). For example, in 1979 a forty-something year-old in the top income quintile was about 6 percentage points more likely to be married that one in the bottom 80 percent. Now the gap is 17 percentage points.

This is hardly surprising. More education and more earners in the home will increase the chances that you make it into the top quintile for your age cohort. But it is noteworthy that the extent to which these different dimensions of advantage overlap has been steadily increasing over time. Along with the increased association between top-quintile income and marriage, the differentials for graduate education and two-earner status have each increased by around 10 percentage points between 1979 and 2014.

Particularly striking is the increase in the “marriage gap” between the upper middle class and the rest. This is an important factor in the transmission of class status to the next generation, since married couples are more likely to stay together, and stable families predict better outcomes for children.

Similarly, the adults with high levels of education are likely to raise children who end up towards the top of the educational distribution. In fact, the intergenerational persistence of education is even greater than of income, as some of our earlier work shows (“The Inheritance of Education”). Almost half (46 percent) the children of parents in the top education quintile end up in the top education quintile themselves. Three in four (76 percent) stayed in one of the top two education quintiles.

F. Scott Fitzgerald famously said: "Let me tell you about the very rich. They are different from you and me.” Ernest Hemingway’s later response was: “Yes, they have more money.” Today what separates the rich from the rest is not just money, but family life, education, zip code, and so on. This is a point made by a number of scholars, including recently both Robert Putnam in Our Kids and Charles Murray in Coming Apart. Our empirical analysis confirms that different kinds of advantage are increasingly overlapping with each other.

The framing of inequality in terms of social class used to feel distinctly un-American. No longer.

Editor’s note: This piece originally appeared in Real Clear Markets.

The BBC is doing something I think is awesome but many of my American friends think is awful: gathering information of the social class background of their recruits. The move is part of an aggressive strategy to promote more diversity both on the airwaves and behind the scenes at the public service broadcaster. The civil service has been moving in the same direction.

Some questions arise:

Race and gender are relatively straightforward characteristics, notwithstanding the recent nonsense over restrooms for transgender people. Defining social class is a much more complex business. Many variables could be included, including occupational status, income or wealth, as well as education or cultural capital.

But the goal here is simply to find a measure that is good enough for the purposes at hand. The BBC asks whether either of your parents has a college degree. This is not a bad approach. Education is an important dimension of social class in itself, and strongly related to others. The BBC is also going to ask whether at any point in childhood the person in question was eligible for free school meals. (The questions are voluntary.)

Such proxy measures are narrow measures of class. But they are better than the current ones, since there are none.

Diversity can benefit organizations by widening the range of viewpoints and perspectives. A mixed team is a better team. Class background may be as important here as other factors.

Take two people of a different race or gender, each raised by wealthy East Coast parents, attending a top-drawer private high school, and graduating from an Ivy League college. They may not be as different from each other as they are from a white man raised by a poor single mother in a small Appalachian town.

The BBC is historically an upper middle class institution: “BBC English” meant a posh accent. The British professions in general have in fact tended to draw from a narrow talent pool. Around 7 percent of students attend private high schools (or “public schools”, in British). But they are strongly over-represented in the top professions, including journalism:

From a broader societal perspective, the persistence of class inequality is of course bad news for upward social mobility.

Simply raising awareness of a potential class bias in hiring and promotions could be valuable. Reforming institutional practices—for example the allocation of internship opportunities—may also help. Broadening the search for talent beyond the marquee brands of higher education is likely to diversify the class background of recruits; the BBC is also moving to both name-blind and institution-blind applications. At the same time, greater support for less traditional hires may help them to succeed.

The U.S. sees itself as a classless society, one reason Americans recoil against monitoring social class. It is an understandable instinct. But the perpetuation of class status is now at least as big a problem in the U.S. as in the UK. Even as white privilege and male privilege have diminished, class privilege has survived. A little more class-consciousness might not hurt.

Politicians and scholars often lament the persistence of poverty across generations. But affluence persists, too. In the U.S. especially, the top of the income distribution is just as “sticky”, in intergenerational terms, as the bottom. The American upper middle class is reproducing itself quite effectively.

Class reproduction is of course driven by a whole range of factors, from parenting and family structure through formal education, informal learning, the use of social networks, and so on. Some are unfair: playing the legacy card in college admissions, securing internships via closed social networks, zoning out lower-income families from our neighborhoods and school catchment areas. (These “opportunity hoarding” mechanisms are the focus of my forthcoming book, Dream Hoarders.)

It is natural and laudable for parents to want their children to prosper. It is also understandable that they’ll use the resources and means at their disposal to try to reduce the chances of their children being downwardly mobile. They are likely to try even harder if the drop looks big, in economic terms.

There is a significant earnings gap between those at the top and those in the middle. But this gap is much bigger in the U.S. than in other nations, and is getting bigger over time:

The cost of falling reflects the particular way in which income inequality has risen in recent years: namely, at the top of the distribution. The relationship between income inequality and intergenerational mobility is a much-disputed one, as regular readers of this blog know well. Overall, the evidence for a “Great Gatsby Curve” is quite weak.

But at the top of the distribution, there could be some incentive effects linking inequality and immobility. As the income gap has widened at the top, the consequences of falling out of the upper middle class have worsened. So the incentives of the upper middle class to keep themselves, and their children, up at the top have strengthened. It looks like a long drop, because it is.

Upper middle class Americans do seem worried. In 2011, while around half of American adults making less than $30,000 per year agreed that “today’s children will lead a better life than their parents,” only 37 percent of those making $75,000 or more were as optimistic.

The greater spending of upper middle class parents on “enrichment activities” is well known; recent evidence suggests the Great Recession did nothing to reduce it. American upper middle class parents are desperate to secure their children a high position on the earnings ladder. This makes sense, given the consequences of downward mobility for their economic fortunes. Inequality incentivizes opportunity hoarding, which reduces social mobility. Time, perhaps, to lower the stakes a little?

This post continues a series begun in 2014 on implementing the Common Core State Standards (CCSS).  The first installment introduced an analytical scheme investigating CCSS implementation along four dimensions:  curriculum, instruction, assessment, and accountability.  Three posts focused on curriculum.  This post turns to instruction.  Although the impact of CCSS on how teachers teach is discussed, the post is also concerned with the inverse relationship, how decisions that teachers make about instruction shape the implementation of CCSS.

A couple of points before we get started.  The previous posts on curriculum led readers from the upper levels of the educational system—federal and state policies—down to curricular decisions made “in the trenches”—in districts, schools, and classrooms.  Standards emanate from the top of the system and are produced by politicians, policymakers, and experts.  Curricular decisions are shared across education’s systemic levels.  Instruction, on the other hand, is dominated by practitioners.  The daily decisions that teachers make about how to teach under CCSS—and not the idealizations of instruction embraced by upper-level authorities—will ultimately determine what “CCSS instruction” really means.

I ended the last post on CCSS by describing how curriculum and instruction can be so closely intertwined that the boundary between them is blurred.  Sometimes stating a precise curricular objective dictates, or at least constrains, the range of instructional strategies that teachers may consider.  That post focused on English-Language Arts.  The current post focuses on mathematics in the elementary grades and describes examples of how CCSS will shape math instruction.  As a former elementary school teacher, I offer my own personal opinion on these effects.

Certain aspects of the Common Core, when implemented, are likely to have a positive impact on the instruction of mathematics. For example, Common Core stresses that students recognize fractions as numbers on a number line.  The emphasis begins in third grade:

CCSS.MATH.CONTENT.3.NF.A.2
Understand a fraction as a number on the number line; represent fractions on a number line diagram.

CCSS.MATH.CONTENT.3.NF.A.2.A
Represent a fraction 1/b on a number line diagram by defining the interval from 0 to 1 as the whole and partitioning it into b equal parts. Recognize that each part has size 1/b and that the endpoint of the part based at 0 locates the number 1/b on the number line.

CCSS.MATH.CONTENT.3.NF.A.2.B
Represent a fraction a/b on a number line diagram by marking off a lengths 1/b from 0. Recognize that the resulting interval has size a/b and that its endpoint locates the number a/b on the number line.

When I first read this section of the Common Core standards, I stood up and cheered.  Berkeley mathematician Hung-Hsi Wu has been working with teachers for years to get them to understand the importance of using number lines in teaching fractions.^[1] American textbooks rely heavily on part-whole representations to introduce fractions.  Typically, students see pizzas and apples and other objects—typically other foods or money—that are divided up into equal parts.  Such models are limited.  They work okay with simple addition and subtraction.  Common denominators present a bit of a challenge, but ½ pizza can be shown to be also 2/4, a half dollar equal to two quarters, and so on. 

With multiplication and division, all the little tricks students learned with whole number arithmetic suddenly go haywire.  Students are accustomed to the fact that multiplying two whole numbers yields a product that is larger than either number being multiplied: 4 X 5 = 20 and 20 is larger than both 4 and 5.^[2]  How in the world can ¼ X 1/5 = 1/20, a number much smaller than either 1/4or 1/5?  The part-whole representation has convinced many students that fractions are not numbers.  Instead, they are seen as strange expressions comprising two numbers with a small horizontal bar separating them. 

I taught sixth grade but occasionally visited my colleagues’ classes in the lower grades.  I recall one exchange with second or third graders that went something like this:

“Give me a number between seven and nine.”  Giggles. 

“Eight!” they shouted. 

“Give me a number between two and three.”  Giggles.

“There isn’t one!” they shouted. 

“Really?” I’d ask and draw a number line.  After spending some time placing whole numbers on the number line, I’d observe,  “There’s a lot of space between two and three.  Is it just empty?” 

Silence.  Puzzled little faces.  Then a quiet voice.  “Two and a half?”

You have no idea how many children do not make the transition to understanding fractions as numbers and because of stumbling at this crucial stage, spend the rest of their careers as students of mathematics convinced that fractions are an impenetrable mystery.   And  that’s not true of just students.  California adopted a test for teachers in the 1980s, the California Basic Educational Skills Test (CBEST).  Beginning in 1982, even teachers already in the classroom had to pass it.   I made a nice after-school and summer income tutoring colleagues who didn’t know fractions from Fermat’s Last Theorem.  To be fair, primary teachers, teaching kindergarten or grades 1-2, would not teach fractions as part of their math curriculum and probably hadn’t worked with a fraction in decades.  So they are no different than non-literary types who think Hamlet is just a play about a young guy who can’t make up his mind, has a weird relationship with his mother, and winds up dying at the end.

Division is the most difficult operation to grasp for those arrested at the part-whole stage of understanding fractions.  A problem that Liping Ma posed to teachers is now legendary.^[3]

She asked small groups of American and Chinese elementary teachers to divide 1 ¾ by ½ and to create a word problem that illustrates the calculation.  All 72 Chinese teachers gave the correct answer and 65 developed an appropriate word problem.  Only nine of the 23 American teachers solved the problem correctly.  A single American teacher was able to devise an appropriate word problem.  Granted, the American sample was not selected to be representative of American teachers as a whole, but the stark findings of the exercise did not shock anyone who has worked closely with elementary teachers in the U.S.  They are often weak at math.  Many of the teachers in Ma’s study had vague ideas of an “invert and multiply” rule but lacked a conceptual understanding of why it worked.

A linguistic convention exacerbates the difficulty.  Students may cling to the mistaken notion that “dividing in half” means “dividing by one-half.”  It does not.  Dividing in half means dividing by two.  The number line can help clear up such confusion.  Consider a basic, whole-number division problem for which third graders will already know the answer:  8 divided by 2 equals 4.   It is evident that a segment 8 units in length (measured from 0 to 8) is divided by a segment 2 units in length (measured from 0 to 2) exactly 4 times.  Modeling 12 divided by 2 and other basic facts with 2 as a divisor will convince students that whole number division works quite well on a number line. 

Now consider the number ½ as a divisor.  It will become clear to students that 8 divided by ½ equals 16, and they can illustrate that fact on a number line by showing how a segment ½ units in length divides a segment 8 units in length exactly 16 times; it divides a segment 12 units in length 24 times; and so on.  Students will be relieved to discover that on a number line division with fractions works the same as division with whole numbers.

Now, let’s return to Liping Ma’s problem: 1 ¾ divided by ½.   This problem would not be presented in third grade, but it might be in fifth or sixth grades.  Students who have been working with fractions on a number line for two or three years will have little trouble solving it.  They will see that the problem simply asks them to divide a line segment of 1 3/4 units by a segment of ½ units.  The answer is 3 ½ .  Some students might estimate that the solution is between 3 and 4 because 1 ¾ lies between 1 ½ and 2, which on the number line are the points at which the ½ unit segment, laid end on end, falls exactly three and four times.  Other students will have learned about reciprocals and that multiplication and division are inverse operations.  They will immediately grasp that dividing by ½ is the same as multiplying by 2—and since 1 ¾ x 2 = 3 ½, that is the answer.  Creating a word problem involving string or rope or some other linearly measured object is also surely within their grasp.

I applaud the CCSS for introducing number lines and fractions in third grade.  I believe it will instill in children an important idea: fractions are numbers.  That foundational understanding will aid them as they work with more abstract representations of fractions in later grades.   Fractions are a monumental barrier for kids who struggle with math, so the significance of this contribution should not be underestimated.

I mentioned above that instruction and curriculum are often intertwined.  I began this series of posts by defining curriculum as the “stuff” of learning—the content of what is taught in school, especially as embodied in the materials used in instruction.  Instruction refers to the “how” of teaching—how teachers organize, present, and explain those materials.  It’s each teacher’s repertoire of instructional strategies and techniques that differentiates one teacher from another even as they teach the same content.  Choosing to use a number line to teach fractions is obviously an instructional decision, but it also involves curriculum.  The number line is mathematical content, not just a teaching tool.

Guiding third grade teachers towards using a number line does not guarantee effective instruction.  In fact, it is reasonable to expect variation in how teachers will implement the CCSS standards listed above.  A small body of research exists to guide practice. One of the best resources for teachers to consult is a practice guide published by the What Works Clearinghouse: Developing Effective Fractions Instruction for Kindergarten Through Eighth Grade (see full disclosure below).^[4]  The guide recommends the use of number lines as its second recommendation, but it also states that the evidence supporting the effectiveness of number lines in teaching fractions is inferred from studies involving whole numbers and decimals.  We need much more research on how and when number lines should be used in teaching fractions.

Professor Wu states the following, “The shift of emphasis from models of a fraction in the initial stage to an almost exclusive model of a fraction as a point on the number line can be done gradually and gracefully beginning somewhere in grade four. This shift is implicit in the Common Core Standards.”^[5]  I agree, but the shift is also subtle.  CCSS standards include the use of other representations—fraction strips, fraction bars, rectangles (which are excellent for showing multiplication of two fractions) and other graphical means of modeling fractions.  Some teachers will manage the shift to number lines adroitly—and others will not.  As a consequence, the quality of implementation will vary from classroom to classroom based on the instructional decisions that teachers make.  

The current post has focused on what I believe to be a positive aspect of CCSS based on the implementation of the standards through instruction.  Future posts in the series—covering the “bad” and the “ugly”—will describe aspects of instruction on which I am less optimistic.