Are Lorenz curves and QQ-plots the same? If not, where are the differences? I read about both of them and they appear to be two terms for the same type of plot / statistical technique to compare distributions. I was not able to find any confirmatory source for this. Perhaps you know?
The Lorenz curve is just a cumulative distribution function for a random variable bounded between 0 and 1, e.g., a proportion. In economics, the Lorenz curve asks, "what fraction of income is earned by the lowest x% of earners?" Typically, it is compared to the uniform distribution over [0,1], a distribution that would arise under perfect equality in income. The Gini coefficient is the area under the perfect equality curve less the area under the Lorenz curve, normalized by the area under the perfect equality curve; note that the area under the perfect equality curve is equal to 0.5.
So, to be clear, while a QQ plot compares two distributions to one another, the Lorenz curve considers only one distribution that has a range over [0,1].