I am just starting out with math in uni for my research so this is a really simple question. I calculated the fraction of number of school enrollments during a policy period from 1991 to 1993 over the total number of enrollments in the sample period - 1981 to 2001 for each province in my country. I then ranked these values and for those provinces with rates of enrollment during policy period greater than the mean of all provinces, the indicator variable will be equal to one and categorized as a High Intensity Province (PI).
I want to formalize this exercise for my research paper and I would like to know if this is the right way to do it. $PI_i = \begin{cases}1~&{\text{ if }}\bar x_i > \Sigma_{i=1}^k \frac{\text{number of enrollments 1991-93}_i}{\text{number of enrollments 1981-2001}_i} \\0~& {\text{other wise.}}\end{cases}\ $