1960s style definitions.
Difference between "concept" and "measurement"
Validity (meaning), Reliability (stability), Precision (fineness)
Level of measurement question. Are the numbers meaningful? How compare across time/countries?
First Generation measures: Sample survey tools
Focus on Transparency International's CPI
What is the meaning of the questions asked? Do they gauge breadth and depth of corruption (my terms, not his)
TI had warned people not to interpret their numbers literally, but people did.
So look for more subtle information
Bribe Payer's Index (BPI)
Usual conclusion. Still more work to do.