Have you ever wondered how much your neighbor has in their 401k plan? If your neighbor works for an oil company it's probably a sizeable account.  Here's an interesting 401k study from Business Week:

Best Three Plans by Account Values

ExxonMobil: $490,000
Saudi Arabian Oil: $450,000
                     Chevron: $370,000

The three richest plans, by average participant balance, are all oil companies. Saudi Arabian Oil, however, has just 2,900 total participants. ExxonMobil has 44,000, and Chevron has 36,000.

Data: BrightScope