Fixing indicator goalposts across decades is required for meaningful time comparisons.

Evidence

The main problem with shifting the goal posts annually is that it precludes meaningful comparisons over time: a country’s HDI could change from year to year for reasons that have nothing to do with its performance. So, this year, we fix “normative” values for life expectancy, adult literacy, mean years of schooling and income. These minimums and maximums are not the observed values in the best or worst-performing countries today but the most extreme values observed or expected over a long period (say, 60 years). The minimums are those observed historically, going back about 30 years. The maximums are the limits of what can be envisioned in the next 30 years. Demographic and medical information suggests that the maximum average life expectancy for the foreseeable future is 85 years. Similarly, recent economic growth rates indicate that the maximum income that the richest countries are likely to achieve by 2020 is $40,000 (in 1990 PPP dollars). — Gary Goertz, Social Science Concepts and Measurement, 879

Categorization

• SHARE: Send to anyone who follows the Human Development Index: its fixed ceiling of 85 years life expectancy and $40,000 income is a normative bet, not an observation.