Diversity and differences in nature and society

Inequality in nature and society

If the title of an article is about "inequality", our brain starts thinking inmediately about equality, with some moral background. It's unavoidable. If the title is "diversity and differences", than we admit it as statement. I would suggest to have a look at this interesting article in PNAS that compares what happens in society and in nature, please forget any previous influence of values.

As a first illustration of the similarities of patterns in nature and society, consider the wealth distribution of the world’s richest individuals compared with the abundance distribution of the Amazon’s most common trees (Fig. 1 A and B). The patterns are almost indistinguishable from one another. For a more systematic comparison, we also analyzed the Gini indices of a wide range of natural communities and societies (Fig. 1 C and D). The Gini index is an indicator of inequality that ranges from 0 for entirely equal distributions to 1 for the most unequal situation. It is a more integrative indicator of inequality than the fraction that represents 50%, but the two are closely related in practice (SI Appendix, section 3). Surprisingly, Gini indices for our natural communities
are quite similar to the Gini indices for wealth distributions of 181 countries (data sources listed in SI Appendix, section 1).

This is only a statement that you can confirm.

 Our analysis suggests that even if all actors are equivalent, in the absence of counteracting forces, there is an intrinsic tendency for significant inequality to arise from multiplicative chance effects. Although the surprising similarity between inequality of species abundances and wealth may have the same roots on an abstract level, this does not imply that wealth inequality is “natural.” Indeed, in nature, the amount of resources held by individuals (e.g., territory size) is typically quite equal within a species.

Now the metaphor has been clarified. Differences in wealth does not imply that are "natural". Fortunately our country is less different now than before. We have moved from a Gini of 33 in 2013 to 31.4 in 2016, quite good. You'll not find this reflected in any newspaper -it seems that this statement does not sells issues-, though these are the official figures.

Estimating health expenditures

Modeling Health Care Expenditures and Use

The skewed distribuition of health expenditures with a large number of 0 observations poses difficulties. A recent article in Annual Review of Public Health explains the details and the right approach, in my opinion.

We compare estimation and interpretation of the effect of a change in insurance policy on health care expenditures using OLS and a two-part model. The two-part model is based on a statistical decomposition of the density of the outcome into a process that generates zeros and a process that generates positive values. A logit or probit model typically estimates the parameters that determine the threshold between zero and nonzero values of the outcome. In general, alternative specifications of the binary choice model (the first part) yield nearly identical results. However, the choice of model for the distribution of the outcome conditional on it being positive (the second part) is critically important. Different models can yield quite different results.We use a generalized
linear model to estimate the parameters that determine positive values. Generalized linear models accommodate skewness in natural ways, give the researcher considerable modeling flexibility, and fit health care expenditures extremely well.

The use of two parts models, and GLM is the standard approach to take into account. The book Health econometrics using Stata is the key reference.

On experts and priorities

Priorización de intervenciones sanitarias. Revisión de criterios, enfoques y rol de las agencias de evaluación

Often I hear that prioritisation of benefits could be solved by evaluation agencies and the appropriate application of cost-effectiveness analysis. As times goes by, I'm convinced that this is a way to avoid if we consider how priorities should be set. In other words, leaving this issue to a technical perspective is not enough. There is a need for a deliberative way to tackle the complexities of prioritisation.
Anyway, if you want to know a review that takes as given the experts view, check this article. If you want to understand the whole issue from a broader perspective, then read the book I quoted in this post some months ago.

 Carlos Diaz at Sala Parés