SANTA CLARA, Calif. — Investors searching for another reason to worry about the American economy found it in Google.

Shares of Google Inc. yesterday slumped nearly 5% to their lowest point in almost a year on fears that even the mighty Internet giant is susceptible to the economic slowdown.

The toxic combination of rising prices, slumping consumer confidence, and slashed business spending have hurt much of corporate America. Yet Google for years remained largely immune to the economic cross-currents. It grew to power during the last recession early this decade and continues to post huge profits.

But investors started souring on the company’s prospects last month and have knocked one-third off its market value this year.

They’re also quick to assume the worst in this skittish market. A research report suggesting that fewer people clicked on Google’s search-engine ads in January was enough to trigger another sell-off yesterday. Google’s shares dropped $22.25 to $464.19 — 38% off its record high of $747.24 reached in November.

“No company is immune from the prospect of an economic slowdown,” Internet software and services analyst with Standard & Poor’s, Scott Kessler, said.

Some analysts and marketing experts raced to Google’s defense, arguing that the market reaction was overblown.

They said the monthly research reports, by Web-measurement firm Comscore Inc., haven’t usually proven good barometers of Google’s financial results. They noted that Google could count on its international users to buffer an American slowdown.

They argued that its status as the clear leader of a booming online advertising market left Google as the most likely Internet company to weather any drop-offs in consumer or business spending.