[seanmcdirmid]

Sorry I guess. I couldn't find Tesla's P/E ratio on Google like I could for the other companies. It is my understanding that they don't report P/E ratios for companies with negative earnings.

And it makes sense: a high P/E ratio indicates high potential. The lower the earnings, the higher the P/E ratio. But if earnings went negative, then the P/E ratio would automatically go negative (since that is how math works, as you say). So if my stock price is $100, and I earn $1, my P/E ratio is 100...so much potential! If I accidentally lost a dollar instead, my P/E ratio automatically becomes -100 even though not much changed in my earnings.

[kbenson]

The interesting thing is that as soon as you go negative, a larger negative P/E is better than a smaller negative P/E, and it's really wonky at earnings close to 0.