Inserting rows and performing calculations

Hello everyone! New here. Hoping someone can help save me to design a macro, use a script, SOMETHING!

I have a cancer dataset from all countries globally from 1990 to 2017 displaying 1 variable, prevalence. The data is displayed as follows:

Code Entity Year Prevalence
AFG Afghanistan 1990 37368.73147
AFG Afghanistan 1991 37785.11432
...
AFG Afghanistan 2017 87681.28407
ALB Albania 1990 19960.99434
ALB Albania 1991 20607.36016

Here's what needs to happen. For every country (231 values), I need to project the prevalence rate out to 2030 using the average annual growth rate from 1990 to 2017.

What is my best strategy to:
Insert 13 rows after each occurance of "2017" in the year column
Fill these rows with the years 2018-2030
Take an average of the annual growth rate for each country
Use this rate to project a prevalence for each country for the years 2018-2030

I have ~some~ experience with Macros and this seems like a problem that a Macro can solve. I just don't quite know how!
Anything helps. Thanks!

Woah. Brilliant! Thank you so much!