Glenn Firebaugh is an American sociologist (born: Charleston, West Virginia) and leading international authority on social science research methods.
Rule 4 advises researchers to replicate, that is, "to see if identical analyses yield similar results for different samples of people" (p. 90).
Inequality indices reflect that fact because they have this common form: where pj weights the units by their population share (necessary in a cross-country analysis, for example, since countries vary in population), and f(rj) is a function of the deviation of each unit’s rj from 1.0, the point of equality.
Firebaugh describes this important turning point in a 1999 lead article in the American Journal of Sociology[4] and in a 2003 book.
Firebaugh’s findings challenged earlier claims that global income inequality continues to rise rapidly.
According to Firebaugh, that claim was based on a flaw: Each country was assigned equal weighting, despite vast differences in population size.
[6] As a result, earlier claims by the United Nations[7] and the World Bank[8] of rapidly rising global income inequality have been modified in their more recent publications.
Researchers are said to commit the ecological fallacy when they make untested inferences about individual-level relationships from aggregate data.
[11] Firebaugh has contributed to this literature by delineating theoretical conditions or rules under which it is possible to infer individual-level relationships from aggregate data.