Hello, I was wondering if there was an easy way to calculate the rate of
change in a variable for an unbalanced panel data set.  Below is a detailed
description in R of what I am asking.  Thank you.  Geoff

#Suppose I have the following unbalanced panel data;

Person <- c(rep('Frank',5), rep('Tony',4), rep('Edward',4));
Year <- c(2005,2006,2007,2008,2009,2005,2006,2008,2009,2006,2007,2008,2009);
Score <- c(55,58,63,23,34,38,56,87,44,32,98,45,56);

Data <- data.frame(Person=Person, Year=Year, Score=Score);
Data;

#Is there a simple way to calculate the Year-to-Year percentage change in
Score that accounts for the missing data?;
#Notice that Tony is missing data for the Year 2007 and Edward is missing
the Year 2005;
#Note as well that we will need to end up losing the Year 2005 in the
calculation;

-- 
Geoffrey Smith
Visiting Assistant Professor
Department of Finance
W. P. Carey School of Business
Arizona State University

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