↳ Bias

August 26th, 2019

↳ Bias

Summer in Brabant


On the pressures of policy-relevant climate science

Without any “evidence of fraud, malfeasance or deliberate deception or manipulation,” or any promotion of inaccurate views, how can bias enter a scientific assessment? In their new book, Discerning Experts, Michael Oppenheimer, Naomi Oreskes, Dale Jamieson, et al explore the pattern of underestimation of the true consequences of climate change.

Climate change's impacts are uncertain; predictions about climate change are difficult to make. Taking an ethnographic approach, Discerning Experts shows how those difficulties, coupled with the nature of the public discourse, and the pressures that come when research is going to be discussed and used in policy, have tilted climate assessment optimistic and cautious.

In a summary of their book, Oreskes et al explain three reasons for the tilt:

“The combination of … three factors—the push for univocality, the belief that conservatism is socially and politically protective, and the reluctance to make estimates at all when the available data are contradictory—can lead to ‘least common denominator' results—minimalist conclusions that are weak or incomplete.”

These tendencies, according to the authors, pertain to the applied research context. The academic context is different: “The reward structure of academic life leans toward criticism and dissent; the demands of assessment push toward agreement.” Link to a summary essay in Scientific American. Link to the book.

  • In an interview, Michael Oppenheimer elaborates on other elements that skew the assessments: the selection of authors, the presentation of the resulting information, and others. Link.
  • In a review of the book, Gary Yohe reflects on his own experience working on major climate assessments, such the IPCC’s. Link.
  • A David Roberts post from 2018 finds another case of overly cautious climate science: models of the economic effects of climate change may be much more moderate than models of the physical effects. To remedy this, “We need models that negatively weigh uncertainty, properly account for tipping points, incorporate more robust and current technology cost data, better differentiate sectors outside electricity, rigorously price energy efficiency, and include the social and health benefits of decarbonization.” Link.
  • Tangentially related: carbon tax or green investment? It’s worth considering not just all possible policy options but also their optimal interactions. A paper by Julie Rozenberg, Adrien Vogt-Schilb, and Stephane Hallegatte concludes, “Optimal carbon price minimizes the discounted social cost of the transition to clean capital, but imposes immediate private costs that disproportionately affect the current owners of polluting capital, in particular in the form of stranded assets.” Link to a summary which contains a link to the unpaywalled paper.
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July 8th, 2019

Model of a Cabin


Examining the college premium

Higher education is widely understood to be a major driver of intergenerational mobility in the United States. Despite the clear (and growing) inequalities between and within colleges, it remains the case that higher education reduces the impact that parental class position has on a graduate's life outcomes.

In an intriguing paper, associate professor of economics at Harvard XIANG ZHOU scrutinizes the implied causal relationship between college completion and intergenerational mobility. Specifically, Zhou uses a novel weighting method "to directly examine whether and to what extent a college degree moderates the influence of parental income" outside of selection effects, seeking to distinguish between the "equalization" and "selection" hypotheses of higher ed's impact on intergenerational mobility.

From the paper:

"Three decades have passed since Hout’s (1988) discovery that intergenerational mobility is higher among college graduates than among people with lower levels of education. In light of this finding, many researchers have portrayed a college degree as 'the great equalizer' that levels the playing field, and hypothesized that an expansion in postsecondary education could promote mobility because more people would benefit from the high mobility experienced by college graduates. Yet this line of reasoning rests on the implicit assumption that the 'college premium' in intergenerational mobility reflects a genuine 'meritocratic' effect of postsecondary education, an assumption that has rarely, if ever, been rigorously tested.

In fact, to the extent that college graduates from low and moderate-income families are more selected on such individual attributes as ability and motivation than those from high-income families, the high mobility observed among bachelor’s degree holders may simply reflect varying degrees of selectivity of college graduates from different family backgrounds."

In sum, Zhou finds that the "selection" hypothesis carries more weight than the "equalization" hypothesis. One implication of this finding is that "simply expanding the pool of college graduates is unlikely to boost intergenerational income mobility in the US." Link to the paper.

  • A 2011 paper by Michael Bastedo and Ozan Jaquette looks at the stratification dynamics affecting low-income students within higher ed. Link. A paper from the same year by Martha Bailey and Susan Dynarski surveys the state of inequality in postsecondary education. Link.
  • An op-ed by E. Tammy Kim in the Times argues for higher-education as a public good. Link.
  • Marshall Steinbaum and Julie Margetta Morgan's 2018 paper examines the student debt crisis in the broader context of labor market trends: "Reliance on the college earnings premium [as a measure of success] is that it focuses primarily on the individual benefit of educational attainment, implying that college is worthwhile as long as individuals are making more than they would have otherwise. But in the context of public investment in higher education, we need to know not only how individuals are faring but also how investments in higher education are affecting our workforce and the economy as a whole." Link.
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