The USA Today study, based on data from S&P Capital IQ, looked at companies that were part of Standard & Poor’s 500 index, with fuel refiner Valero coming out on top in the analysis by reaping $3.4 million of revenue per worker during the first quarter.

Phillips 66, an integrated downstream company, which is a considerable refiner and gas producer, clocked up a $2.7 million revenue return per worker.

Healthcare-linked AmerisourceBergen, the only non-energy company in the top eight, took third spot with $2.3 million of revenue per worker while pipeline player Oneok was next placed with $1.6 million, shale player EOG Resources followed with $1.5 million and refiner Tesoro’s workers averaged $1.4 million.

Workers at ExxonMobil came in seventh, generating an average of $1.3 million of revenue each during the first quarter, while Marathon Oil workers were next with an average of $1 million.

Looking at this measure of productivity among well-known stocks in other fields, the average worker at Apple yielded $568,443 of revenue while the average Netflix worker brought in $583,949 of revenue during the March quarter.