The index includes things like health care, access to education, personal safety, sanitation, human rights, and so forth, and combines them all into a single number. This number doesn’t change a lot from year to year, and from 2011 to 2016 it went up by 0.34 in the United States. Since then, however, it’s fallen by an astonishing 1.06 in just four years. We now rank 28th in the world, just behind Greece.
Note that this isn’t an economic index. The US is still one of the richest countries in the world. We just aren’t using those riches to make much social progress.
This is really not a surprise. Social progress does not register in the consciousness of Trump and the Republicans. What drives them is power and greed.
There is always one major problem when you take multiple measures and then weight them to arrive at a single number. That single number enables you to compare different countries but that number also depends on how you weight the individual items to get the composite result and that introduces a lot of subjectivity because if you change the weighting, you can get a different rank order of countries. So the more meaningful use of such data is to take a longitudinal approach and see how, keeping the weighting system unchanged, the number changes over time, rather than take a snapshot approach and compare different countries at one time.