WASHINGTON (CNN) -- President Bush on Wednesday signed the Economic Stimulus Act of 2008, calling it a "booster shot" for the American economy.
"The bill I'm signing today is large enough to have an impact, amounting to more than $152 billion this year, or about 1 percent of the GDP (gross domestic product)," the president said in the brief ceremony in the East Room of the White House.
The government hopes the measure, which will send most Americans tax rebate checks by May, will either prevent a recession or make one relatively brief.
The package also includes tax breaks for equipment purchases by businesses, as well as payments to disabled veterans and some senior citizens.
The bipartisan measure moved through Congress at relative break-neck speed, going from initial discussions to enactment in less than four weeks.
The package will pay $600 to most individual taxpayers and $1,200 to married taxpayers filing joint returns, so long as they are below income caps of $75,000 for individuals and $150,000 for couples. There is also a $300 per child tax credit.
Watch Bush sign stimulus bill into law »
The rebates will put about $120 billion in the hands of individuals in the hope that they will spend it and boost a faltering U.S. economy.
Economists generally agree that the economy should see a boost from the rebate checks. But most also agree that the full impact will be less than the total value of the stimulus package.
That's because some recipients are expected to save their rebates or use them to pay down credit cards or other debt instead of spending it. In addition, some consumers may spend their rebates on imported items, which would provide a more limited lift to the U.S. economy.
"My guess is that of the $110 billion to $120 billion of tax rebates, about half will go to U.S. products and services," said David Wyss, chief economist for Standard & Poor's.
There also are questions about whether the stimulus will actually be the key to ending or preventing a recession.
Treasury Secretary Henry Paulson said last week that the Internal Revenue Service planned to send the rebate checks to about 130 million Americans.
"They're going to be getting ready to get checks out, and believe me, they will. ... And this is largely going to be done by the time summer's over. And so we're going to move quickly and make a difference," he said
Bush praised the quick work of the House and Senate and urged Americans not to "overreact" to the current economic troubles.
"In the past seven years, the system has absorbed shocks: recession, corporate scandals, terror attacks, global war; yet the genius of our system is that it can absorb such shocks and emerge even stronger," he said. "In a dynamic market economy, our economy will prosper and it will continue to be the marvel of the world." E-mail to a friend 
CNN's Adam Levine contributed to this report.
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