Did BP Shares Fall or Rise on Tuesday? Yes

BP sign
BP sign

As strange as it sounds, shares in beleaguered oil spiller BP (BP) both fell and rose in Tuesday trading. You see, the energy giant's home exchange is the London Stock Exchange, where BP lists its ordinary shares. They closed down 1.7% at 302.9 pence (or about $4.56) a share.

When we talk about BP in the context of the U.S. equity market, we're talking about something called BP's American depositary shares (ADS), which are listed on the New York Stock Exchange (NYX). ADS and American depositary receipts are a common way for a foreign company to list its stock on an American exchange.

Each share of BP listed in London equals six of the company's shares on the NYSE -- and the New York listing rose by 2.3% to $27.67 on Tuesday. Divide $27.58 by six and you get $4.61, or the about the same value as BP's home-exchange shares in dollars.

When we say BP has lost $100 billion in market capitalization since April 20 on account of the Gulf oil disaster, we're talking about the value of the shares listed on the NYSE. But the market cap in pounds sterling has taken an equivalent beating. Interestingly, shares in London have held up slightly better than their U.S. counterparts by about 2 percentage points. Still, as should be expected, both the London and New York versions of BP's stock have tanked in tandem (see chart).