Compensation?

A Wall Street Journal article on April $4,2021,$ "Amazon's Labor Unrest May

Page $29$

Show at the Margins," described Amazon as having "thin margins by tech standards," noting that Amazon's revenue$/$employee was only about one$-$fifth as large as "peers" such as Alphabet $($Google$),$ Apple, Facebook, and Microsoft. The Journal seemed to be suggesting that if unionization is successful at Amazon $($on a significant scale, i$.$e$.,$ beyond the one current location where a union organizing drive is taking place$),$ that Amazon's labor costs will increase and it cannot afford that if its margins are already thin. Why would the Journa$/$ use these tech companies as peers? Isn't Walmart a better peer comparison?

To get better insight, go to the most recent annual reports $($form $10-$k$),$ readily available on the web, and compute revenue per employee for Walmart and Amazon. $($At Amazon, use net sales as revenue.$)$ Also, compute the ratio of operating income to revenue by business segment for Walmart and Amazon. $($Revenue per employee is not possible to compute based on the Amazon annual report.$)$ Each company has three business segments.

QUESTIONS:

How does the ratio of operating income to revenue compare across segments within and across the companies? Focusing on Amazon, how do these operating income$/$revenue ratios differ across its segments?