What You Need to Know About SEC's Investigation of Pimco

On Tuesday, the Wall Street Journal reported that the SEC has been questioning whether Pacific Investment Management Company, more commonly known as Pimco, has been improperly valuing bonds in one of its portfolios to boost the fund's returns.

While it's too early to tell whether the SEC will ultimately allege Pimco did anything improper, here are three key takeaways:

This is another black eye for Bill Gross.

Bill Gross, often referred to as "the bond king," is one of Wall Street's highest-profile investors. His flagship fund, Pimco Total Return, is a mainstay in many 401(k) retirement plans. And with $220 billion in assets, the fund is one of the largest investment portfolios in the world.

Recently, however, Gross's star has waned. Misplaced bets on Treasury bonds have hurt Total Return's performance. Over the past year the fund has finished in the bottom tenth of its category, according to Morningstar.

Gross also recently endured a public split with protege and presumptive successor, Mohamed El-Erian, who left Pimco in March. Since then Gross, long a media darling, has even started to get bad press. This includes a much-talked about Wall Street Journal story making him seem like a difficult boss. Then there was a Bloomberg Businessweek cover story about Gross that asked, "Am I Really Such a Jerk?"

An SEC investigation only adds to his troubles.

The investigation highlights a long-running dispute about bond ETFs.

The SEC investigation appears to be targeting not Pimco's flagship Total Return mutual fund but a smaller $3.6 billion exchange-traded fund version of Total Return created in 2012. The ETF version has won some fans, in part by outperforming its older sibling. You can read Money's take on the pros and cons of the ETF version here.

Bond ETFs in general are wildly popular. Investors have poured in more than $180 billion since the financial crisis. But they've had their share of problems, and the latest controversy won't help. To understand why, you have to grasp a bit of the nitty-gritty:

Exchange-traded funds are baskets of securities that trade on an exchange like a stock. Their original appeal to investors had a lot to do with their transparency. Investors can look up at any moment precisely what all of the securities in the ETF are worth. By contrast, traditional mutual funds only value their holdings once a day.

This extra transparency is pretty easy to accomplish when ETFs hold stocks, since most stocks trade every day and the prices are published by exchanges. With a little computing power, stock prices can be tallied up and the total published right away.

That's not necessarily true of the bond market, where many individual bonds rarely change hands daily.

As a result bond ETF values, while still published continually, are really estimates based on trades of similar (but not necessarily precisely matching) bonds. The upshot is that while stock ETFs almost always trade at prices that are within a few pennies of their putative value, bond ETFs aren't as reliable.

When traders who are buying bond ETFs disagree with official price estimates about the value of the bonds in the ETF's portfolio, the ETFs can appear to trade at odd-looking prices.

The industry has endlessly debated what should be regarded as the "true" price. The Pimco controversy, as you see below, appears to have a lot to do with whether actual trades or some other estimate of a bond's value should be regarded as the "true" price.

The investigation shows how complicated bond investing can be.

Pimco's actions may have actually helped, not hurt, investors, based on the Wall Street Journal's description. Still, this doesn't mean the SEC is wrong to explore its actions.

Here's what seems to be at issue: Bonds are typically traded in large blocks. When bonds aren't part of these blocks they can be difficult -- read expensive -- to trade. Apparently, Pimco went around buying up small blocks of bonds, known as "odd lots," at discounts. Pimco then marked their prices upwards using estimates of their values derived from larger blocks of bonds.

Is there anything wrong with this? It's hard to tell because we can only speculate about how Pimco felt justified in doing it.

If Pimco really couldn't resell the bonds at the new, higher prices it seems off base. But it also seems plausible the bonds might genuinely be worth more in Pimco's hands than they were in the hands of whoever sold them.

Perhaps with Pimco's enormous size it's able to combine these small odd lots of bonds into a larger "round" lot, making the sum worth more than the parts. Or perhaps like a broker in any market, Pimco's contacts and influence mean it can count on reselling the bonds at a higher price than the original owner could. The devil is in the details, which we don't yet know.

One other thing to keep in mind. Even if this strategy was a smart one, the SEC may still be right to pursue the case. Allowing bond managers to think they have too much leeway with bond valuations is asking for trouble. Pimco's investors may have benefited in this particular instance.

But regulators are probably right to be sticklers even if they did. Don't forget that during the financial crisis big banks effectively hid billions in losses by using questionable methods to value bonds.