兩年前用網上數據推了一下，有些過時了，但是個參照數，大廠朋友眾多指證

https://bbs.wenxuecity.com/znjy/5645705.html

"85% of engineers do not promote again past L4. For the 15% that’s left, 2–5 years later, they promote again. 85% of engineers do not promote again past that point. For the 15% that’s left, 2–5 years later, they promote again. And so on" -- From https://www.quora.com/profile/Dean-Jackson-3

有人通過LinkedIn 做了統計， 大約總共有950 L6, 300 L7, 110L8, 27 L9, 4 L10。 這個統計是2015年做的有些out of date，但是數量級應該差不多。那麽L7& +總共有500人左右. 這些人都要求 significant impact and delivered mission critical projects. 非常有要求。

“Level 7- Principal Engineer / Level 8 - Distinguished Engineer: These are much higher impact roles. Such engineers have owned and delivered on very large mission-critical projects for Google (Think significant search engine/ads optimizations that have in a verifiable way, impacted Google positively). They are responsible for initiating, driving, technically designing, implementing and productionizing high impact ideas at Google with the help of teams if needed.”