NEW YORK (CNN/Money) - Back up the truck and get on board, because on the momentum train, the caboose is as good as the engine.

Yes, momentum -- that charming investing style that propelled stocks higher in the late 1990s -- is back. Professional investors, fretful over not having taken part fully in the stock market rally, are playing an increasingly desperate game of catch up. They're putting money into the market's most volatile stocks and as these stocks rise, they're putting more money into them. So far there's been nothing to suggest that in the weeks to come it won't be more of the same. (Click here for a line-up of the week ahead's key events.)

"Near term, the market is playing the momentum game," said Brett Gallagher, head of U.S. equities at Julius Baer Investment Management. "If you're a relative performance manager, it's hard not to play along."

Most fund managers -- Gallagher included -- are judged not by how well they've done in absolute terms, but by how they've done against their peers. As a result standing against the crowd and being wrong can have severe consequences. Going with the crowd and losing money, on the other hand, doesn't carry much of a penalty.

"If you're not in the market, you're dead now if you're a fund manager," said Kirlin Securities chief market strategist Tony Dwyer. "There are clearly people doing some chasing now."

Run down the list of stocks in the S&P 500 that have done best in the past month and you'll see that it ain't exactly the cream that's been rising to the top. Rather, you'll see that a bunch of second-tier techs (like Broadcom) and not-so-safe utilities (like El Paso) have put on the biggest moves. And guess what? These stocks had big moves in the previous month, too. What better way is there to make money than to invest in what's working now?

Clearly this sort of stuff is dangerous, and fun as it is while it lasts, you need to be prepared to beat a quick retreat. Dwyer thinks the market could be in store for a fairly vicious rotation out of the stocks that have been running most into safer shares. He points out that mutual funds don't have all that much money to play with -- at last count just 5 percent of their portfolios were in cash -- which means there are limits to how much they can buy. Moreover, as the quarter comes to a close and companies begin to warn on earnings (there are always some), mutual fund managers may opt to take some of the risk out of their portfolios.

This assumes, however, that individual investors don't decide to play along. After outflows for the first three months of the year, mutual funds have been seeing modest inflows. Should these flows continue to mount -- in other words, should individual investors begin trying to get in on the momentum game -- then look out above. And keep one finger hovering over the sell button.

The main economic event of the coming week will be Thursday's release of retail sales data for May. Economists don't expect it to be very good, but the market may not care.

"There is a lot of evidence that the economy is having trouble moving ahead," said Morgan Stanley economist Bill Sullivan. "Yet the equity market is convinced that the environment is going to improve."

Economists surveyed by Briefing.com expect that retail sales picked up by just 0.2 percent last month after dropping 0.1 percent in April. Clearly, the big post-war rebound in spending that everybody was expecting didn't come. This quarter personal consumption is tracking for its slowest growth since 1993.

The hope is that spending is on the cusp of a rebound. There will be 25 million child tax credit checks hitting America's mailboxes at the end of next month. Thanks to super low rates, mortgage refinancing activity has hit new highs, helping to pad home owners' pockets.

The downside? The ranks of the unemployed have swollen to 9 million, and many workers are wary that their job will be the next to go. There's no guarantee that just because you give people cash they'll spend it.

• Monday, wholesale inventories for April get released. An incredibly volatile series, inventories have remained fairly low as businesses play it safe. Economists expect inventories rose by 0.2 percent after rising 0.5 percent in March.
• Wednesday the Beige Book, the Fed's collection of anecdotal evidence on the economy, gets released. A good way to get a snapshot of what's going on around the country.
• May retail sales come out Thursday. Economists expect they gained 0.2 percent after April's 0.1 percent decline.
• Business inventories for April, due out Thursday, are expected to show a 0.3 percent gain. In March they gained 0.4 percent.
• April trade figures come out Friday. Economists expect the trade deficit fell to $41.9 billion from March's $43.5 billion.
• The key measure of inflation at the wholesale level, the producer price index, gets released Friday. Economists expect it dropped by 0.1 percent in May after falling 1.9 percent in April. Excluding energy, it's expected to come in flat versus April's 0.9 percent drop.
• The University of Michigan's preliminary reading on its consumer sentiment index is expected to come in at 94, up from April's 92.1.