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  • Strange results with -mi impute-

    Hi everyone,

    I am new to multiple imputation. I have a large dataset (60,000+ observations) with data from 7 years. Data for a variable (that I called "missing_variable" in the example below) in the first two years are missing due to collection issues. I am trying to impute it using a dozen other variables in the data (including the variables that I am using in my analytical model).

    Here is my code so far:


    Code:
    mi set wide 
    mi xtset, clear 
    mi register imputed missing_variable
    
    mi impute pmm missing_variable control1 control2 control3.... control12 i.year , add(5) rseed(25000) noisily dots force knn(30) bootstrap
    I've been using pmm because most of these variables are not normally distributed.

    The results are a little strange. About 80% of imputed values are equal to a single number: 1.115355. That is true for all 5 imputed variables.

    Anyone have an idea of what might be going on here?

    Jack



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