Ideally, we would measure the things we value directly. Unfortunately, we often value things that are difficult to measure, so that we must instead measure other variables that are closely related to what we do value. For instance, we may try to measure the impact of an intervention on someone’s
health , because improving health tends to improve well-being. Although we ultimately care about well-being rather than health, the latter is a relatively good measure of the former, which is hard to measure directly.
Katja. 2015. Apples and oranges? Some initial thoughts on comparing diverse benefits.
A discussion of various means of measurement and comparison.
Wikipedia. 2016. Happiness economics.
A discussion of the measurement of happiness.