A report released Thursday by the Washington-based Center on Budget and Policy Priorities, a liberal advocacy group, concludes that a similar referendum adopted by Colorado voters in 1992 -- known as the Taxpayer Bill of Rights or TABOR -- stifled that state's economic growth and drained revenues from state coffers.

"Any short-term gain that was correlated with the passage of TABOR in the first five years after TABOR was adopted was completely wiped out and partially reversed for the long term," said Therese McGuire, a Northwestern University economist and the report's co-author. "TABOR has not had a positive effect on Colorado's economy."

If the Michigan initiative makes it to the ballot and is approved by voters in November, it would limit the annual growth in state spending to a formula based on the growth in the state's population and the inflation rate.

Any revenues collected that exceed spending limits would be split equally between taxpayers and the state's rainy day fund, a feature not included in the Colorado amendment. The rainy day fund would be capped at 10 percent of the state's annual budget or about $2.7 billion.

"The Michigan (amendment) is more flexible," said Kurt O'Keefe, spokesman for the Michigan Stop Overspending (SOS) Committee, which is behind the petition drive. "It puts boundaries up, and then it asks the state to operate within the limits. To me, it's a confidence question. Do we have faith in the people to make decisions about the size of government? Or do we have faith in the state?"

The SOS Committee has until July 10 to file 317,757 signatures with the Secretary of State's office, which will determine whether there are sufficient signatures to place the question on the fall ballot.

Another section of the proposed ballot initiative would prevent state lawmakers from collecting a state-funded pension if they are elected after January 2007. They would be eligible for a a self-funded 401(k).

Backers of the petition drive say the Colorado constitutional amendment returned millions of dollars to taxpayers and businesses over the last decade and boosted that state's economy, adding that Colorado is doing far better than Michigan. For example, they point to the fact that Colorado's unemployment rate in January was 4.7 percent compared with Michigan's 6.2 percent.

"Colorado got hit with a record drought and the demolition of its tech bubble in the early part of this century, and it's still managed to recover from it," said Ken Braun, an analyst with the Mackinac Center for Public Policy, a free-market policy group in Midland.

The report concedes that Colorado might have benefited from TABOR in the 1990s, but its fortunes changed once the economy turned sour after 2000. The TABOR restrictions forced some tough budget choices. Over the last 14 years, Colorado dropped from 35th to 49th in the nation in K-12 education spending as a percentage of personal income, the report noted.

In response to budget concerns, last November Colorado voters suspended TABOR for five years, postponing the annual taxpayer refunds to increase the amount of revenue available for state programs.

Opponents say Michigan already has a protection built into the state Constitution. In 1978, taxpayers approved a constitutional amendment limiting state revenue collections to 9.49 percent of the state's personal income.

"We have a revenue limit called the Headlee Amendment," said Sharon Parks, a spokeswoman for the Michigan League for Human Services, an advocacy group for the poor. "We are currently $5.8 billion below our limit. Headlee is working fine in Michigan. We don't need this."

Three states -- Maine, Ohio and Oklahoma -- already have Colorado-like spending limits before voters this fall. Another eight states, including Michigan, have petition drives under way.