Hello wonderful Stata helpers,
I know this is less Stata-specific and more conceptual, but I would appreciate some clarification if possible.
I am building a fragility index. In the end I want there to be a number that represents each country's fragility in a given year, with a high number meaning very fragile and a low number meaning pretty stable. For the most part, the indicators that make up the index follow this pattern. For indicators that had data that meant the opposite, I simply reversed the scale. They were all measured on a scale of 0 - 4, so when necessary I use the following method:
sum varname
gen varname_rev = (max(varname)+1) - varname

example code:
sum v2caviol
gen v2caviol_rev = 5 - v2caviol
(side question: even though the indicator scale was 0-4, some of the actual observations can go as low as negative 2 and as high as 5, I think from a normalization process. Is this method of reversing still valid? or should I go with the observed max?)

Main question #1: For an indicator such as school enrollment, the scale is from 0 to 100 percent. Can I still use the same method?
Main question #2: For an indicator such as life expectancy, there is no predetermined scale, so this method seems completely inappropriate. The observed maximum is 85.3 but I think there's something wrong with subtracting life expectancy from 86.3 - I don't think the indicator would convey the same information as before. So if I can't do this scale reversal, I worry that including this indicator will just add noise, since in general higher life expectancies correlate with less fragility and higher stability. When I aggregate all these indicators into one index, is there a way to include life expectancy that accommodates its meaning?

Any insights would be very much appreciated!!!