Reuters, yesterday afternoon:

In London, BP shares closed down 5 percent, against a drop of 2 percent in the STOXX Europe 600 Oil and Gas index.

In New York, the company’s American depositary shares fell more than 6 percent. BP shares have lost about a third of their value since the crisis erupted.

Actually, it’s a lot more than “about a third”.

On April 19, the day before the Deepwater Horizon oil rig went kaboom, BP’s shares closed at $59.48.

Yesterday’s close was $34.68, for a decline of 41.7%. I imagine BP’s stockholders have trouble seeing 41.7% as about the same as 33.3%.

To put it in perspective, a 33.3% decline would correspond to a share price of $39.67. A drop in the stock price from $39.67 to $34.68 would wipe out one-eighth of the stock’s remaining value. It would be widely described as a plunge. Reuters, gods bless their journalistic accuracy, calls it rounding error.

 
*** Update, 12:40 p.m. ***

I really should be more careful what I write.

Here I was, just this morning, blithely trotting out a hypothetical example of a 12.5% plunge in BP’s stock price.

And, lo and behold, as of 12:39 p.m. PDT, BP’s shares have fallen more than 15% to $29.22.

I don’t know about you, but I see a nice little corporate extortion racket in my future.