Hello @Chai2 and welcome to the SAS Support Communities!
I've just found the 2016 blog post "Examine patterns of missing data in SAS" by Rick Wicklin where the term "Metropolitan Relative Weight" (which is what MRW stands for) is linked to a scientific paper. The definition of MRW starts at the bottom of the first page of that paper.
Hello @Chai2 and welcome to the SAS Support Communities!
I've just found the 2016 blog post "Examine patterns of missing data in SAS" by Rick Wicklin where the term "Metropolitan Relative Weight" (which is what MRW stands for) is linked to a scientific paper. The definition of MRW starts at the bottom of the first page of that paper.
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