In short order, the image of sovereign wealth funds went from global predator to high-profile patsy. Several of these huge, government-created investment pools bet billions of dollars on big-name financial institutions and other marquee concerns and notched equally large losses in the aftermath of the 2008 crisis. Then news pretty much stopped.

A new study by London-based research group Preqin Ltd. shows that the total value of sovereign wealth funds at the end of March topped $4.62 trillion, a more than 50% increase over 2008. That jump comes after a fairly static two years. At this time last year, sovereign wealth funds totaled a bit less than $4 trillion, Preqin estimates.

The study serves as a stark reminder that sovereign wealth funds remain a powerful force globally. That potency, many analysts maintain, will only increase over time.

"Their impact on global capital markets, their impact on direct investment, will expand and continue to grow," says Patrick Schena, a senior fellow at the Center for Emerging Market Enterprises at Tufts University's Fletcher School. The center two years ago created the Sovereign Wealth Fund Initiative.

Mind you, the gains, while impressive, are nowhere near some of the pronouncements made before the global crisis. In early 2008, a few seers predicted sovereign wealth funds would reach $12 trillion by 2015 and would dominate mega-investments.

"They were way off," says Edwin Truman, senior fellow at the Peterson Institute for International Economics, a former assistant secretary of the U.S. Treasury for International Affairs and the author of the 2010 book "Sovereign Wealth Funds: Threat or Salvation?"

Most funds experienced a rapid return to earth from the lofty heights experienced before the crisis. One fund, Dubai World, racked up so many bad real estate investments that it was forced to declare a debt moratorium in 2010 and restructure its debt a year later.

The existing portfolios of most sovereign wealth funds lost amounts in the 20% range, Truman says, proving they were subject to the same contractions as pension funds and endowments. He adds that even the multibillion-dollar bets some funds made in financial institutions such as Lehman Brothers Holdings Inc., Merrill Lynch & Co. and UBS, which led some critics at the time to raise the specter of a new wave of mercantilism, is evidence of a lack of exceptionalism. As Truman says, "A lot of other investors made the same kinds of mistakes."

In the years since, most -- though not all -- sovereign wealth funds dialed back the highest-profile investments. "Generally, [deals] are less flashy," Schena says. "What funds are doing is less sexy."

The Preqin study can make it sound as if sovereign wealth funds are a re-energized force. In fact, they never really disappeared, and they remained a potent capital source throughout the crisis. Some, such as Russia's, were used to offset budgetary gaps. Ireland's fund was tapped to shore up the country's collapsed banks.

Preqin ran the numbers on some 63 different funds. Abu Dhabi Investment Authority tops the list, with $627 billion under management, followed by Norway's Government Pension Fund, with $596 billion. Two Chinese sovereign wealth funds -- State Administration of Foreign Exchange and China Investment Corp. -- come next. Together they total a bit under $1 trillion.

At the other end, São Tomé and Principe's fund comes in at a scant $6 million. Mauritania has funded only $34 million.

Accurately and thoroughly charting this investment class is tough. Many funds lack rudimentary transparency. Some sovereign wealth fund managers refuse to reveal even the overall size of their funds. That includes large, sophisticated funds such as Government of Singapore Investment Corp., which will say only that funds total "well over" $100 billion. (Preqin estimates the total at $247.5 billion, which ranks GIC as the seventh-largest sovereign wealth fund in the world.)

Preqin places an "unknown" label next to the size of one fund in the United Arab Emirates and two each in Ghana and Oman.

When it comes to total numbers, "no one knows," says Michael Maduell, the president of the Sovereign Wealth Fund Institute, a Las Vegas-based research and analytics firm. He cites some sovereign wealth funds in which even senior staff are kept in the dark. His institute estimates current global totals at "pretty much $5 trillion," but concedes it could easily be above that.

Those who follow sovereign wealth funds caution that the term itself encompasses a wide range of funding sources and investment mandates. Some split the universe into two: There are funds that place an emphasis on long-term savings, and others that are geared to revenue or budgetary stabilization.

Another way to delineate is through funding source. Petroleum and other natural resource revenues underwrite some funds, notably those in the Middle East. Others are primed by budgetary outlays or by foreign exchange surpluses.

Lastly, the funds boast varied investment objectives that can go beyond the desire to simply maximize returns or provide a hedge against inflation or currency fluctuations. Schena cites France, which initiated its Fonds Stratégique d'Investissement in 2008. According to Preqin, the fund now totals $25 billion. The stated goal of the fund is to increase competitiveness of French business through minority stakes in small and medium-sized companies. "It's defensive," Schena says. "These are decidedly inward forms of investment."

In assessing sovereign wealth fund gains, rising oil prices is a major factor. Preqin estimates that a bit more than half of the assets being injected into the funds comes from revenue derived from the petroleum and natural gas industry. As Maduell explains, many petroleum-based sovereign wealth funds have established a benchmark price for oil. If the price exceeds that benchmark, money gets "shoved in faster" to the funds.

By now, the use of a sovereign wealth fund to further either long-term savings goals or budgetary stabilization efforts is an established mechanism. "It's more and more accepted as a construct," says Schena.

New entrants suggest one reason why the global totals have jumped. In the past four years, France, Kazakhstan, Brazil, Ghana and Malaysia have formed new funds. Since 2006, 12 new funds have been created; taken together thay have a current market value of at least $500 billion, Schena estimates. Several other countries are investigating starting their own. Israel is in advanced stages. India has made noises, as has the Philippines.

With the exception of Venezuela, which has its own unique set of problems, governments are no longer tapping sovereign wealth funds to shore up faltering finances as they did during the global financial crisis. That use of funds certainly took place, and in large numbers, although it's difficult to fully quantify the activity. "It is impossible to tell with any certainty how much a decline in assets was due to the covering of governmental deficit or other factors," Preqin's Alex Jones writes in an e-mail exchange. "However, there is certainly anecdotal evidence to suggest that this is the case."

Jones, who authored the report, elaborates: "For those institutions that do offer transparent performance data it is clear that some have had very positive returns in recent years, but the major source of money flowing into some sovereign wealth funds can also be put down to individual governments deciding to build their funds back up following the impact of the crisis."

Preqin cites Russia, which siphoned off tens of billions of dollars from its Reserve Fund. Last year, Moscow reversed course and injected cash into the fund, although the commonly held view that the government deposited $50 billion is only speculation.

Norway and Chile also replenished funds. China Investment Corp. hadn't received new funds from the government for several years. In March, a CIC executive told local media Beijing had kicked in $30 billion in 2011, with more to come.

Sovereign wealth funds have become a critically important source of capital for alternative assets including hedge funds and private equity. The Preqin study underscores that trend. According to Pre-qin, 57% of all sovereign wealth funds now invest in private equity, although that represents a modest two percentage-point drop from 2011. (The smallest funds tend to avoid private equity.) The Kuwait Investment Authority allocates a full 10% of its almost $300 billion in funds under management to private equity. That $30 billion allocation means the Kuwaitis are possibly the single-largest private equity limited partner in the world.

Sovereign wealth funds can provide the foundation of a large private equity fundraising. Preqin cites Apax Partners LLP's Apax Europe VIII, which made its first close in March. Apax raised €4.3 billion ($5.6 billion) of a targeted €9 billion fund, €900 million of which came from Australian, Singaporean and Chinese sovereign wealth funds.

Preqin also notes Hellman & Friedman LLC's newest fund, which totaled $8.8 billion, $1.8 billion above target size. Alaska Permanent Fund Corp., Singapore's GIC and the New Zealand Superannuation Fund all invested. Sovereign wealth funds "will become an increasingly important source of capital for the private equity industry," says Philip Hammarskjold, Hellman & Friedman's CEO. "The $64,000 question is whether that increase will be sufficient to offset declines in other sources of PE capital."

In this age of low interest rates, a desire for heightened returns is certainly critical. However, for some sovereign wealth funds, investing in private equity transcends simple investment gains, say a number of analysts. Part of this may be a reaction to some of the busted direct investments made before the onset of the crisis. "It makes sense not trying to manage all their money by themselves," says Truman. "In some sense, they are outsourcing their decisions."

They also can learn along the way. As sovereign wealth funds beef up staff focused on private equity and other alternative asset classes, they turn to their general partners for more than just advice. "Sovereign wealth funds can get training and technical assistance," says Truman. Funds "can learn from [private equity] expertise."

While that may eventually lead to more and more direct investments, it's already creating different forms of partnerships. Some sovereign wealth funds now co-invest alongside their private equity general partners. And as they gain expertise, sovereign wealth funds increasingly chafe about the fees they pay private equity firms, which is no big surprise. That most likely will also lead to different kinds of arrangements with their general partners, analysts believe. "We're seeing increased interest in custom-tailored approaches," says Michelle Davidson, a managing partner at advisory services firm TorreyCove Capital Partners LLC.

Managed accounts are one possibility; investments in the private equity firms themselves are another. Davidson cites as a model the February announcement by EIG Global Energy Partners LLC that it is selling a minority stake to CIC.

A more selective use of private equity firms is one possible outcome. Sovereign wealth funds will favor the biggest names in private equity or those that specialize in one kind of investment strategy like EIG Partners. "The biggest change is a focus on risk management," says Davidson.

According to Preqin, 28% of sovereign wealth funds invest in private equity funds-of-funds. That's an 8 percentage-point gain from a year earlier. However, the use of funds-of-funds is less desirable and is increasingly limited to the smallest or newest sovereign wealth funds.

"Real estate is big," says Maduell. That makes sense, given a fund's long-term investment horizon, concerns about inflation and a desire for a stable cash flow. According to Preqin, Abu Dhabi Investment Authority, Qatar Investment Authority, CIC and Singapore's GIC lead the pack. Each has allocated more than $20 billion to real estate.

That exposure is increasingly global. The Preqin study cites a joint venture between Singapore's GIC and the Canada Pension Plan Investment Board to invest in Brazilian real estate. That also reflects what Davidson sees as increased interest among sovereign wealth funds in emerging-markets real estate.

Real estate investments can also showcase what Maduell believes to be a growing trend among sovereign wealth funds: club deals. Last December, GIC teamed up with CIC to pay ¥122.6 billion ($1.5 billion) for logistics properties in Japan, Preqin details.

Infrastructure offers even longer-term opportunities for many sovereign wealth funds. "They're happy to trade liquidity for higher returns over a longer term," says Schena.

Abu Dhabi alone has allocated more than $30 billion to this asset class, according to Preqin. The Kuwait Investment Authority invests a minimum $100 million in infrastructure funds that must exceed $1 billion, according to Preqin. The research firm cites as an example of a direct investment in infrastructure a Kuwaiti €600 million investment in December 2010 for a 4.8% stake of Areva SA, the French nuclear energy company. Qatar's sovereign wealth fund spent a similar amount for a 5% stake in Veolia Environnement SA earlier that year. "You will continue to see huge deals in infrastructure," says Davidson.

Despite some notable losses, sovereign wealth funds haven't turned their backs on direct investments. A study by Monitor Group reported that in 2010, sovereign wealth funds invested a total of $52.7 billion in 172 publicly reported deals. That represented a 23% decrease in total value from 2009, but a 50% increase in volume. In other words, sovereign wealth funds are investing in more, but smaller, deals.

"Investors on this scale invest in scale," says Schena, but he adds: "You're less likely to see massive deals."

Even financial institutions remain fair game. However, active sovereign wealth fund investors such as Singapore's Temasek Holdings Pte. Ltd. are now focusing on banks closer to home. On April 16, Temasek announced it was buying $2.3 billion worth of shares in Industrial and Commercial Bank of China (Asia) Ltd. from Goldman, Sachs & Co. (Temasek lost almost $5 billion with its precrisis investments in Merrill Lynch, which was taken over by Bank of America Corp. Temasek sold its BofA stake in early 2009.)

The range of transactions is enormous. Abu Dhabi's Mubadala Development Co., for example, invested in Sony Corp.'s $2.2 billion acquisition of EMI Group Ltd.'s publishing assets, an acquisition just cleared by the European Union. Last year, Mubadala announced that it would invest in an advanced flight-training facility in Abu Dhabi.

Then there's the Qatar Investment Authority. In 2010, it paid $2.2 billion for the legendary London department store Harrods and an additional $1.1 billion for the Raffles Hotel in Singapore. In mid-April, eyebrows rose again when the authority filed with the Securities and Exchange Commission to report that it had amassed a 5.2% stake in Tiffany & Co., the iconic jeweler. "Certain funds are oriented to so-called trophy properties," says Schena tactfully.

Investment rationales among sovereign wealth funds run the gamut from geographic diversity to good old-fashioned opportunity. Many analysts believe the continued euro-zone crisis could provide a boost to sovereign wealth fund investments in Europe. There's speculation that Chinese sovereign wealth funds in particular are actively assessing new investments in Europe. "There's an opportunity to take what assets they want," Maduell says, adding that he believes sovereign wealth funds will also play a key role in refinancing European corporates.

"Big deals are always going to happen," Maduell says, adding that the crisis taught sovereign wealth funds some lessons. "They are going to be more selective. They are going to be more cautious. They're going to think about it more."