R-squared is not percentage but is proportion.

[vasili111]

On page 191 I read:

An R-squared indicated the percentage of variation...

R-squared is not a percentage but is proportion.

More information can be found by googling: https://www.google.com/search?q=rsqured

[anthonydb]

I've seen it defined both ways. This, for example, is from Duke University:
https://people.duke.edu/~rnau/rsquared.htm

And this is from Penn State University:
https://online.stat.psu.edu/stat462/node/95/

I'll check with some statisticians and try to get a consensus.

[vasili111]

In the Penn Sate University link that you have provided they are converting r-squared to percentages after multiplying it by 100. That means that original value is proportion. Screenshot: