I think both Chris and I get that definition of ‘markup’ from Jonathan Nitzan’s class. We can quibble with names (some people call profit/sales the ‘profit margin’) but I think the metric itself is unquestioningly of value. That does not mean we shouldn’t explore other metrics.
About the offset fiscal years, that does seem to raise issues, especially if you are interested in comparing data for a specific year. But as the time frame of analysis expands, I think these minor accounting differences are not that important.
We are beholden to the data that is reported, and the accounting quirks on which it is based. But since you raise the question, now you make me think about how other databases treat fiscal years. I’ve never looked to see if Compustat reports the dates covered by each company’s fiscal year. Something to think about, especially when doing fine grain analysis.