Discrete returns versus log-returns I read this link and it is very helpful. 

However, if log-returns are easier for time-aggregation, then why do economists work with discrete returns e.g. in GDP growth?
I would say people usually use log-returns for continuous data (although no data is really continuous, not even tick data). And discrete returns when your data is discrete. In the case of GDP, you only get the data every 3 months, so that is as discrete as it gets.