yup, I was the retail analyst for Macquarie Bank for 6 years. I did this analysis on domestic listed and non listed retailers vs global peers and gross margins globally are pretty similar when compared by industry (adjusting for differences in IFRS and US accounting etc i.e. what is COGS vs what is not COGS).
So what this means is that gross margins for any group of retailers by category are similar +/-3%.
Off top of my head a study i did showed...