Improvements that boost value by percentage terms

[Babek Sandhar]

Hey all, 

I've been looking for the data to support this but it's hard to find at the moment. I'm wondering what improvements would you guys consider the most important and which improvements increase the house value the most in percentage terms?

I'd say exterior landscaping, kitchen, bathroom, windows, doors/garage doors, etc. Anything that's aesthetically pleasing. But does anyone have any data or research that shows the average percentage of increase per renovation item. I'm really curious if it's possible to obtain this type of information, even if it's in a limited capacity.