What are the similarities and differences? To no avail, I tried ODO and this Wordreference.com post.
{verb} 1[.0]. Make or become better:
1.2. [no object] (improve on/upon) Achieve or produce something better than:
Footnote: I encountered this issue while reading Principles of Microeconomics, 7 Ed, 2014, by NG Mankiw, who applies Defn 1.0 on p 11:
Governments Can Sometimes Improve Market Outcomes.
But arrestingly, on p13, Mankiw instead applies Defn 1.2:
To say that the government CAN improve on market outcomes ... does not mean that it always WILL.