Dear Statalister,

I am currently working with data which include patents, patent classes and year. Here is dataex of my data:

Code:
* Example generated by -dataex-. To install: ssc install dataex
clear
input int year long number_of _patents int class

2000 5   1
2000 6   2
2000 7   3
2000 3   4
2001 9   1
2001 8   2
2001 4   3
2001 12  4
2001 5   5

end

This means that in 2000 there were 5 patents in class 1, 6 patents in class 2, 7 patents in class 3 and 3 patents in class 4.

What I intend is to find Peason correlation of patent distribution between two consecutive years , namely between vector a(5 6 7 3) and vector b(9 8 4 12 5). The more similar patent distributions between two consecutive years are, the less environmental turbulence is present.

Thanks in advance for any help.

Best regards, Farid