For investors firmly focused on macroeconomic risks from a possible default in the euro zone to china overheating or the U.S. recovery stalling, BP’s travails are a stark reminder that micro risks have a bite all their own.

Many asset managers will have been caught off guard by the costs — both monetary and political — that have undermined bp since it started leaking crude into the gulf of mexico.

How much they have suffered will depend largely on what style of investor they are. The biggest hit will likely have been taken by passive investors, those who buy into a stock index and simply track it.

But the broad appeal of bp as one of the world’s largest corporate giants will have meant that other, more active investors will also have been hurt, even if their flexibility will have allowed them to soften the blow.

BP’s case is particularly graphic because as a giant company it makes up a large portion of the various stock indexes, including the FTSE 100, that institutional investors track or use as a benchmark.

That means that both active and passive investors will have.

It was worth more than 8 percent of the FTSE in mid-April. With its share price having lost some 40 percent of its value since April 21 this is now down below 6 percent.

The most obvious victims of this are pension funds, many of which have large amounts of money in passive tracker or index funds.

Figures from Britain’s national association of pension funds suggest that the recent bp fall may have wiped more than 4 billion pounds ($6.19 billion) from its members’ coffers.

This, remember, would come on top of losses to the index as a whole.

These investors are also now worried about U.S. pressure on bp not to pay out its dividend later in the year. It accounts for some 12-13 percent of the UK’s dividend payouts, a particular blow to funds seeking income rather than capital gain for investors.

ACTIVE TOO

In some ways this is the bill for investing passively. Funds that simply buy an index benefit when it rises and suffer when it doesn’t.

“They own what’s in the index. That’s the point of them,” said Andrew Clare, professor of asset management at cass business school.

BlackRock, the huge U.S. investment house, says the number of pension fund mandates simply tracking indexes has risen recently as markets have become volatile.

But this is just one end of a polarization that has seen others become more active than they were. The middle ground of being mildly active is being deserted, blackrock says.

The bp pain, meanwhile, is bound to have hit active investors as well, particularly those who “hug a benchmark” or trade closely to one seeking to outperform it by a point or two.

These investors can be underweight bp within their portfolio, but still have to own a fair share of it.

Given that the ftse 100 is used as a proxy for world growth by many investors — some 56 percent of its companies’ revenues come from non-UK sales — many of those who were hurt also will be foreign investors.

PROTECTION

The silver lining for more active investors is that depending on how they are structured they can protect themselves from micro risk.

“With an active manager you are less likely to have overweights in such big stocks,” said Tristan Hanson, multi asset strategist at Ashburton in Jersey.

Ashburton has internal rules that preclude too much exposure to a single corporate risk.

Its funds can have no more than 5 percent of their money in one share, but in practice, it is a lot less than that. Hanson said that Ashburton’s typical big holdings are only 1.5 percent to 2 percent of a portfolio.

James Bristow, a global equities portfolio managers with blackrock, also reckons that investors get the best protection from micro risk by not having too many constraints in what they invest in.

“You give yourself the best chance to outperform if you are flexible in your portfolio,” he said.

Flexibility allows a fund to get out of a troubled company quickly, particularly if the share is highly liquid as BP’s is. It also allows managers to balance the risk of something like the oil spill happening against a variety of factors.

And a micro risk, while hugely damaging for investors, tends not to be as bad for them when they hit as a macro one.

“The company ones are not going to affect the whole portfolio,” said Cass’s Clare.