It is likely not a surprise to most experts that education quality in rural Latin America lags far behind the region’s urban areas. Even though robust growth over the past decade has been fundamentally based on the commodities sector — oil, gas, copper, gold, soybeans and others — there has been little impact on education in these areas.

In fact, urban residents have a 26 percent higher graduation rate than those living in rural areas, another troubling sign of the disconnect in the transition from school to work. That statistic comes from a recent research paper by Inter-American Development Bank (IDB) specialists Marina Bassi, Matias Busso and Juan Sebastian Munoz, which seeks to more fully explain Latin America’s most important education trends.

That paper, “Is the Glass Half Empty or Half Full? School Enrollment, Graduation and Dropout Rates in Latin America,” is the first comprehensive comparative analysis of graduation and dropout rates across Latin America. In it, the authors employed 113 household surveys in 18 Latin American countries over a two decade period from 1990 to 2010.

In my conversation with author Marina Bassi, she highlighted the increased graduation rates as a major discovery of their research. “We knew that access had improved, but what surprised us was the improvement in graduation, which happened in all of the countries that we studied,” she pointed out. Indeed, according to the report, the percentage of the secondary school age population that dropped out before graduation fell from 41 percent in the early 1990s to 30 percent today.

But the bad news: These measures of economic improvement are anemic compared with developed countries in Europe and Asia. Chile is one of the few standouts in the region, with graduation rates approaching those of developed nations; region-wide, only 60 percent of those who start secondary school actually finish. Chile was also one of only two countries (the other being Costa Rica) that significantly reduced its urban-rural divide over the past two decades.

Unfortunately, while the report provides us with a wealth of data, the root causes of these dynamics are largely unexplored. The authors leave us with unanswered questions about what approaches have worked, and which policy choices underperforming countries should be making.

Bassi, Busso and Munoz do clearly describe the factors that correlate with improved education, including increased public expenditure and increased primary school enrollment. But they fail to explain how to get there — for instance, why governments spending more money doesn’t necessarily translate into better education or fewer dropouts.

For instance, the authors imply that one potential policy improvement would be legislation to change the mandatory school age. Yet the evidence here is mixed at best, with countries where there has been no change in this regard, such as Colombia, producing some of the most dramatic improvements in the region.

The IDB report highlights several other persistent problems. The gender performance gap is one such issue that often does not receive enough attention. Indeed, the dropout rate is much higher among boys than girls, and over the decades covered by the study, that gap only increased, rising from six to nine percent.

Finally, the report explores how socioeconomic conditions are perhaps the most important single factor influencing the education any given individual will receive. The numbers are not encouraging: “Students from the highest income quintile have a secondary school graduation rate 33 percentage points higher than students from the lowest income quintile.”

And what’s more, that gap has only gotten worse region wide, increasing by seven percentage points since 1990. The fact that poorer students and poorer regions often have access only to the lowest quality education makes the cycle of inequality very difficult to break.

Again, the authors don’t clarify what types of policies could arrest these negative trends. They do argue that the Conditional Cash Transfer (CCT) programs popularized by Brazil’s Bolsa Escola and Bolsa Familia have been effective in improving graduation rates. However, even these programs may not have much impact on overall inequality, as the study found that in Brazil, “The graduation gap between the highest and lowest income students increased by 20 percentage points, indicating that the benefits mainly affected the richest groups.”

What is clear, however, is that improving graduation rates, and thus improving the school-to-work transition, continues to be one of the most difficult challenges faced by Latin American education systems. For this reason, the IDB’s important work in this area should help raise awareness and advance a much needed debate.