After decades of neglect, Latin American governments are increasingly focusing on urban slums. What often spurs their policy interventions is a desire to counter violent criminality leaking out from the poor marginalized slums controlled by gangs into the city centers the better-off residents want to keep safe. But tackling the socioeconomic dynamics of slums -- the trap of poverty, discrimination, lack of public goods and social services, and rule by nonstate actors -- is not only complex, but also costly. Governments, elites, and middle classes tend not to want to spend resources on slums. Effective policies have to be sustained for decades, and political will and tax revenues for such complex state-building are frequently scarce.

Focusing on a discreet intervention – providing low-cost housing – becomes tempting. Rarely is it sufficient. The condition of the buildings alone is not what makes a slum a slum. Moving residents from slums to better low-cost housing has encountered systematic challenges not just in Latin America, but also in other places where it has been tried, such as Kenya. Instead, policies need to focus on broader community dynamics, including public safety, legal job creation with sufficient income, human capital development, and robust connectivity of slums to economically-thriving areas, something residents of the latter often don’t want.

Paradoxically, real estate dynamics can have pernicious effects. If broader pacification does take hold and public safety in slums increases, some slum areas can become desirable real estate with vast development possibilities. Developers may well seek to buy the land by offering “better” low-cost housing to slum residents to get them to move. Since many slum residents do not have title to their residences, forced displacement also occurs, albeit under the cloak of being nice to the poor.

Instead of being limited to the provision of alternative residences, policies to address slums need to be about inclusion, economic growth, safety, and connectivity of slums with the thriving city parts, and accountability of city-governance authorities.

This commentary was originally published by the Inter-American Dialogue’s Latin America Advisor. 

Earlier this month, the College Board released SAT scores for the high school graduating class of 2015. Both math and reading scores declined from 2014, continuing a steady downward trend that has been in place for the past decade. Pundits of contrasting political stripes seized on the scores to bolster their political agendas. Michael Petrilli of the Fordham Foundation argued that falling SAT scores show that high schools need more reform, presumably those his organization supports, in particular, charter schools and accountability.* For Carol Burris of the Network for Public Education, the declining scores were evidence of the failure of polices her organization opposes, namely, Common Core, No Child Left Behind, and accountability.

Petrilli and Burris are both misusing SAT scores. The SAT is not designed to measure national achievement; the score losses from 2014 were miniscule; and most of the declines are probably the result of demographic changes in the SAT population. Let’s examine each of these points in greater detail.

It never was. The SAT was originally meant to measure a student’s aptitude for college independent of that student’s exposure to a particular curriculum. The test’s founders believed that gauging aptitude, rather than achievement, would serve the cause of fairness. A bright student from a high school in rural Nebraska or the mountains of West Virginia, they held, should have the same shot at attending elite universities as a student from an Eastern prep school, despite not having been exposed to the great literature and higher mathematics taught at prep schools. The SAT would measure reasoning and analytical skills, not the mastery of any particular body of knowledge. Its scores would level the playing field in terms of curricular exposure while providing a reasonable estimate of an individual’s probability of success in college.

Note that even in this capacity, the scores never suffice alone; they are only used to make admissions decisions by colleges and universities, including such luminaries as Harvard and Stanford, in combination with a lot of other information—grade point averages, curricular resumes, essays, reference letters, extra-curricular activities—all of which constitute a student’s complete application.

Today’s SAT has moved towards being a content-oriented test, but not entirely. Next year, the College Board will introduce a revised SAT to more closely reflect high school curricula. Even then, SAT scores should not be used to make judgements about U.S. high school performance, whether it’s a single high school, a state’s high schools, or all of the high schools in the country. The SAT sample is self-selected. In 2015, it only included about one-half of the nation’s high school graduates: 1.7 million out of approximately 3.3 million total. And that’s about one-ninth of approximately 16 million high school students.  Generalizing SAT scores to these larger populations violates a basic rule of social science. The College Board issues a warning when it releases SAT scores: “Since the population of test takers is self-selected, using aggregate SAT scores to compare or evaluate teachers, schools, districts, states, or other educational units is not valid, and the College Board strongly discourages such uses.”  

TIME’s coverage of the SAT release included a statement by Andrew Ho of Harvard University, who succinctly makes the point: “I think SAT and ACT are tests with important purposes, but measuring overall national educational progress is not one of them.”

SAT scores changed very little from 2014 to 2015. Reading scores dropped from 497 to 495. Math scores also fell two points, from 513 to 511. Both declines are equal to about 0.017 standard deviations (SD).^[i] To illustrate how small these changes truly are, let’s examine a metric I have used previously in discussing test scores. The average American male is 5’10” in height with a SD of about 3 inches. A 0.017 SD change in height is equal to about 1/20 of an inch (0.051). Do you really think you’d notice a difference in the height of two men standing next to each other if they only differed by 1/20^th of an inch? You wouldn’t. Similarly, the change in SAT scores from 2014 to 2015 is trivial.^[ii]

A more serious concern is the SAT trend over the past decade. Since 2005, reading scores are down 13 points, from 508 to 495, and math scores are down nine points, from 520 to 511. These are equivalent to declines of 0.12 SD for reading and 0.08 SD for math.^[iii] Representing changes that have accumulated over a decade, these losses are still quite small. In the Washington Post, Michael Petrilli asked “why is education reform hitting a brick wall in high school?” He also stated that “you see this in all kinds of evidence.”

You do not see a decline in the best evidence, the National Assessment of Educational Progress (NAEP). Contrary to the SAT, NAEP is designed to monitor national achievement. Its test scores are based on a random sampling design, meaning that the scores can be construed as representative of U.S. students. NAEP administers two different tests to high school age students, the long term trend (LTT NAEP), given to 17-year-olds, and the main NAEP, given to twelfth graders.

Table 1 compares the past ten years’ change in test scores of the SAT with changes in NAEP.^[iv] The long term trend NAEP was not administered in 2005 or 2015, so the closest years it was given are shown. The NAEP tests show high school students making small gains over the past decade. They do not confirm the losses on the SAT.

Table 1. Comparison of changes in SAT, Main NAEP (12^th grade), and LTT NAEP (17-year-olds) scores. Changes expressed as SD units of base year.

 *p<.05

Petrilli raised another concern related to NAEP scores by examining cohort trends in NAEP scores. The trend for the 17-year-old cohort of 2012, for example, can be constructed by using the scores of 13-year-olds in 2008 and 9-year-olds in 2004. By tracking NAEP changes over time in this manner, one can get a rough idea of a particular cohort’s achievement as students grow older and proceed through the school system. Examining three cohorts, Fordham’s analysis shows that the gains between ages 13 and 17 are about half as large as those registered between ages nine and 13. Kids gain more on NAEP when they are younger than when they are older.

There is nothing new here. NAEP scholars have been aware of this phenomenon for a long time. Fordham points to particular elements of education reform that it favors—charter schools, vouchers, and accountability—as the probable cause. It is true that those reforms more likely target elementary and middle schools than high schools. But the research literature on age discrepancies in NAEP gains (which is not cited in the Fordham analysis) renders doubtful the thesis that education policies are responsible for the phenomenon.^[v]

Whether high school age students try as hard as they could on NAEP has been pointed to as one explanation. A 1996 analysis of NAEP answer sheets found that 25-to-30 percent of twelfth graders displayed off-task test behaviors—doodling, leaving items blank—compared to 13 percent of eighth graders and six percent of fourth graders. A 2004 national commission on the twelfth grade NAEP recommended incentives (scholarships, certificates, letters of recognition from the President) to boost high school students’ motivation to do well on NAEP. Why would high school seniors or juniors take NAEP seriously when this low stakes test is taken in the midst of taking SAT or ACT tests for college admission, end of course exams that affect high school GPA, AP tests that can affect placement in college courses, state accountability tests that can lead to their schools being deemed a success or failure, and high school exit exams that must be passed to graduate?^[vi]

Other possible explanations for the phenomenon are: 1) differences in the scales between the ages tested on LTT NAEP (in other words, a one-point gain on the scale between ages nine and 13 may not represent the same amount of learning as a one-point gain between ages 13 and 17); 2) different rates of participation in NAEP among elementary, middle, and high schools;^[vii] and 3) social trends that affect all high school students, not just those in public schools. The third possibility can be explored by analyzing trends for students attending private schools. If Fordham had disaggregated the NAEP data by public and private schools (the scores of Catholic school students are available), it would have found that the pattern among private school students is similar—younger students gain more than older students on NAEP. That similarity casts doubt on the notion that policies governing public schools are responsible for the smaller gains among older students.^[viii]

Writing in the Washington Post, Carol Burris addresses the question of whether demographic changes have influenced the decline in SAT scores. She concludes that they have not, and in particular, she concludes that the growing proportion of students receiving exam fee waivers has probably not affected scores. She bases that conclusion on an analysis of SAT participation disaggregated by level of family income. Burris notes that the percentage of SAT takers has been stable across income groups in recent years. That criterion is not trustworthy. About 39 percent of students in 2015 declined to provide information on family income. The 61 percent that answered the family income question are probably skewed against low-income students who are on fee waivers (the assumption being that they may feel uncomfortable answering a question about family income).^[ix] Don’t forget that the SAT population as a whole is a self-selected sample. A self-selected subsample from a self-selected sample tells us even less than the original sample, which told us almost nothing.

The fee waiver share of SAT takers increased from 21 percent in 2011 to 25 percent in 2015. The simple fact that fee waivers serve low-income families, whose children tend to be lower-scoring SAT takers, is important, but not the whole story here. Students from disadvantaged families have always taken the SAT. But they paid for it themselves. If an additional increment of disadvantaged families take the SAT because they don’t have to pay for it, it is important to consider whether the new entrants to the pool of SAT test takers possess unmeasured characteristics that correlate with achievement—beyond the effect already attributed to socioeconomic status.

Robert Kelchen, an assistant professor of higher education at Seton Hall University, calculated the effect on national SAT scores of just three jurisdictions (Washington, DC, Delaware, and Idaho) adopting policies of mandatory SAT testing paid for by the state. He estimated that these policies explain about 21 percent of the nationwide decline in test scores between 2011 and 2015. He also notes that a more thorough analysis, incorporating fee waivers of other states and districts, would surely boost that figure. Fee waivers in two dozen Texas school districts, for example, are granted to all juniors and seniors in high school. And all students in those districts (including Dallas and Fort Worth) are required to take the SAT beginning in the junior year. Such universal testing policies can increase access and serve the cause of equity, but they will also, at least for a while, lead to a decline in SAT scores.

Here, I offer my own back of the envelope calculation of the relationship of demographic changes with SAT scores. The College Board reports test scores and participation rates for nine racial and ethnic groups.^[x] These data are preferable to family income because a) almost all students answer the race/ethnicity question (only four percent are non-responses versus 39 percent for family income), and b) it seems a safe assumption that students are more likely to know their race or ethnicity compared to their family’s income.

The question tackled in Table 2 is this: how much would the national SAT scores have changed from 2005 to 2015 if the scores of each racial/ethnic group stayed exactly the same as in 2005, but each group’s proportion of the total population were allowed to vary? In other words, the scores are fixed at the 2005 level for each group—no change. The SAT national scores are then recalculated using the 2015 proportions that each group represented in the national population.

Table 2. SAT Scores and Demographic Changes in the SAT Population (2005-2015)

The data suggest that two-thirds to three-quarters of the SAT score decline from 2005 to 2015 is associated with demographic changes in the test-taking population. The analysis is admittedly crude. The relationships are correlational, not causal. The race/ethnicity categories are surely serving as proxies for a bundle of other characteristics affecting SAT scores, some unobserved and others (e.g., family income, parental education, language status, class rank) that are included in the SAT questionnaire but produce data difficult to interpret.

Using an annual decline in SAT scores to indict high schools is bogus. The SAT should not be used to measure national achievement. SAT changes from 2014-2015 are tiny. The downward trend over the past decade represents a larger decline in SAT scores, but one that is still small in magnitude and correlated with changes in the SAT test-taking population.

In contrast to SAT scores, NAEP scores, which are designed to monitor national achievement, report slight gains for 17-year-olds over the past ten years. It is true that LTT NAEP gains are larger among students from ages nine to 13 than from ages 13 to 17, but research has uncovered several plausible explanations for why that occurs. The public should exercise great caution in accepting the findings of test score analyses. Test scores are often misinterpreted to promote political agendas, and much of the alarmist rhetoric provoked by small declines in scores is unjustified.