Phoebe

I've just added the data into the main discussion thread, but I'll just put a link to it here as well [Happiness_Gini_allcountries.xlsx](https://github.com/QuantEcon/lecture-python-intro/files/14380908/Happiness_Gini_allcountries.xlsx) I've linked the data sources in the thread...

Sorry I didn't see this earlier @Jiarui-ZH @SylviaZhaooo. I believe that comment was referring to a discussion between John and I about the difference between linearity and homogeneity of degree...

Further comments by @mbek0605: - [x] Add axes labels (p_{t+1} and p_{t}) to the 45-degrees plot in 23.4