A quick, interesting way to gauge the health of tech companies is to look at their revenue per employee.

Is management actually growing the business by investing headcount? Or just treading water?

The answers to those questions for Google and Amazon might surprise you.

The best way to do look up this metric is to go to Wolfram Alpha and enter a query like this: "[company name] revenue per employee over the past [X] years."

Here are some charts on some big name tech companies.

Yahoo revenue per employee over the past 10 years:

Google revenue per employee over the past 10 years:

Amazon revenue per employee over the past 10 years:

Microsoft revenue per employee over the past 10 years:

Apple revenue per employee over the past 10 years:

Facebook revenue per employee over the past 3 years:

Twitter revenue per employee over the past 3 years:

LinkedIn revenue per employee over the past 4 years: