Mutual fund giant Fidelity Investments, of Boston, plans to add more than 500 jobs to its work force in Rhode Island starting early next year.

The move, announced Thursday by Governor Carcieri and confirmed by a Fidelity spokeswoman, will mean additional employment for Rhode Island, which has a jobless rate of 12.1 percent, the highest since at least 1976.

The jobs will be transferred from other locations to Fidelity’s campus in Smithfield, which currently employs about 2,300 people, company spokeswoman Anne Crowley said.

Thus, if all goes according to plan, Fidelity will end up employing about 2,800 people in Smithfield, an increase of about 22 percent from the current level.

Carcieri hailed the development. “It’s great news. It’s fantastic news,” he said in a telephone interview Thursday.

“We’re going through a tough spell right now,” and the addition of jobs, particularly from a company like Fidelity, will bring a boost to Rhode Island’s economy, he said.

Crowley declined to say how much the jobs would pay, but Carcieri said that “virtually all” the jobs at Fidelity’s Smithfield campus are well paying, many of them averaging between $50,000 and $60,000 a year.

“They’ve always been, on average, very, very attractive in terms of wage levels,” said Carcieri, who described Fidelity’s Smithfield campus as a kind of “brain center” for the company.

The move is part of a broader reorganization of Fidelity’s work force that generally involves the company’s four principal New England locations: Boston and Marlborough, Mass., Merrimack, N.H., and Smithfield, Crowley said.

As part of that reorganization, some workers will transfer to a given location while others will transfer out.

For example, some workers now in Smithfield will be moved to other Fidelity locations, Crowley said.

But when the transfers are completed, Fidelity’s Smithfield operations will see a net gain of more than 500 jobs, she said. The transfers to Smithfield will start “around the first quarter or so” of 2010, Crowley said.

At about the same time, Fidelity’s Boston operations will see a net gain of more than 500 jobs, while the company’s Marlborough site will experience a net loss of about 950 jobs, she said.

The moves mainly involve Fidelity’s “personal and workplace investing division.” The company’s largest division, it accounts for about 20,000 of Fidelity’s 39,000 employees worldwide, Crowley said.

The unit handles a variety of tasks for the company, including direct investment, Fidelity’s online retail brokerage operation, and the company’s retirement-savings operation, which includes administering 401(k), 403(b) and other employer-sponsored retirement-savings plans, she said. (Fidelity manages about $1.36 trillion in assets, including money held in retirement plans.)

Mark Higgins, dean of the University of Rhode Island’s College of Business Administration, said that the addition of jobs to Fidelity’s Smithfield campus represents “great news for the State of Rhode Island.”

He said that the net increase in jobs will provide “a much-needed boost to the state’s economy,” and shows that Fidelity is committed to its Rhode Island operations.

The new jobs will mean additional income tax, sales tax and other revenue for the state, which has struggled of late mainly because of a drop in tax revenue brought on by the global recession.

Higgins also suggestd that some Fidelity workers might decline transfers, which could result in job openings in Smithfield for Rhode Islanders.

Crowley said that the reorganization is the result of an internal review of the company’s site strategy, which includes better aligning certain groups of employees.

“This is a broader decision than just Rhode Island,” she said. Among the factors that the company weighed in its decision was vacant space that Fidelity has available at its Smithfield and Boston sites, she said.

Asked whether Rhode Island’s tax policy and overall business climate was a factor, Crowley said, “Certainly we also look to have a positive business climate in any state we locate in, and Rhode Island has contributed to that.”

Carcieri earlier this year proposed a number of changes to the state’s tax structure, including a phase-out of the corporate income tax and a reduction in the state’s individual income tax rates.

In the end, the General Assembly rejected most of Carcieri’s tax-cutting plans, and took a series of steps to close a $590-million state budget deficit for the year that began July 1.

But legislators elected to keep in place an alternative method for calculating one’s Rhode Island individual income tax, a method known as the flat-tax option.

Carcieri said on Thursday that the flat tax is one of the factors that Fidelity weighed in its decision to transfer additional jobs to Rhode Island.

“A real issue for them was the flat tax, and I’ve had that discussion with senior people” at Fidelity, Carcieri said.

In general, a taxpayer calculates Rhode Island individual income tax using either the regular system or the flat-tax system.

The regular system currently lets a taxpayer claim a variety of deductions, exemptions and credits, as well as favorable tax treatment of capital gains, but carries tax rates as high as 9.9 percent – one of the highest top rates in the country.

The flat-tax method generally prohibits the use of deductions, exemptions, credits and favorable capital gains treatment, but does provide a flat-tax rate. The rate is 6.5 percent for this year, 6 percent for 2010, 5.5 percent for 2011 and later years.

Carcieri supports the flat-tax method, partly because it makes Rhode Island more competitive from a tax standpoint with its neighboring states. (Massachusetts, for example generally has a flat tax rate of 5.3 percent.)

The high tax rates under Rhode Island’s regular tax system “have always been an impediment to getting some of [Fidelity’s] senior people here,” Carcieri said.

When Rhode Island’s flat-tax system is fully phased in, “We’re going to look very competitive” with Massachusetts and other states, Carcieri said.

A group known as TransformRI ran a series of advertisements in recent weeks promoting Carcieri’s tax-cutting proposals.

Carcieri on Thursday declined to identify contributors to the group, saying that contributors were guaranteed anonymity, and are not required by law to be disclosed.

ndowning@projo.com