Millions of people use Google's search engine every day to find the answers to questions. Today, they'll turn to the company itself in search of information about a particularly burning matter: Is online advertising helped or hurt by the economic downturn?

The disagreement is as wide as the stakes are high. Some argue that these hard times are bad enough that they will spare no sector. Others, noting that internet companies stood at the epicenter of the upheaval in 2001, say the internet will be spared this time. If anything, a recession would speed up the shift in ad dollars from other media since online ads are generally cheaper.

Why not ask the company that has become almost synonymous with online advertising? Unlike most public companies, Google never gives any hints in the form of earnings guidance. So in recent months, as uncertainty and expectations alike piled up, investors have turned to other metrics—and they haven't liked what they've seen.

Beating Up on Google Who's duping whom in a dustup over the F.C.C.'s recent wireless frequencies auction? Read More

The trouble with those alternative metrics is that they don't always agree. There are multiple research firms measuring market share, and they deliver contradicting statistics.

Hitwise, for example, says Google has a 67 percent share of the search market, while comScore reads it at 60 percent.

Depending on which ratings service you believe, Google is either leaving Yahoo in the search dust, or Yahoo is finally gaining on Google.

Those looking for a fresh angle thought they found it when comScore revealed data on its sponsored clicks. Consumers clicking through to such revenue-generating links dropped 7 percent in January compared with December and were flat over the past 12 months. They fell even further in February.

That data overlooked the simple fact that the first quarter is seasonally slow and that the decline in paid clicks happened because Google had started factoring out accidental clicks. This move, meant to benefit advertisers, was potentially evidence of how smart Google had gotten about user activity. Yet all that was overshadowed by investors' hunger for a metric to hang their hats on.

Aiding those bulls, the paid-click declines ended in March. Some analysts looking for a strong quarter from Google noted that reversal to make their case.

"The latest data for March doesn't move the needle much in terms of expectations for the quarter," said Douglas Anmuth of Lehman Brothers. He argued that the decline in ad-click growth earlier this year can be chalked up to fewer clicks in the name of better results.

Other analysts aren't so sure. Brian Bolan of Jackson Securities lowered his Google estimates in part because of the early comScore numbers. And Jason Helfstein of Oppenheimer, while maintaining his outperform rating on Google, acknowledged that the decline "could also be due to fewer clicks by consumers slowing their spending or by advertisers requesting fewer paid clicks."

Both are persuasive arguments. Google will have to give evidence today that its two months of declining clicks this year came in the name of more efficient ads. Without that, bears could gain the upper hand.

But Google also has the chance to set a positive tone for the rest of the tech earnings season (a role that traditionally belonged to Yahoo, which won't report until next Tuesday).

If it can show beyond a doubt that online ads are so far resilient to the economic turmoil, it could help rally tech stocks for the next few months.