Study trims value of DNC

A new study suggests that the Democratic National Convention will be worth $28 million less to Boston's economy than convention boosters and city officials originally estimated.

The Beacon Hill Institute estimates that convention delegates and other visitors will pour $122 million into the city over six days in July. The study's authors said that number validates the convention as a significant economic generator, but their bottom line is smaller than the $150 million estimate floated in a similar study commissioned by the city and Democratic officials and used to help persuade the business community to donate cash to the effort to land the convention.

Yesterday, convention organizers defended their estimate, saying the new study's methodology was flawed and accusing the Beacon Hill Institute of being partisan.

''The quality of their research is suspect," said Angus McQuilken, a spokesman for the Democratic National Convention Committee. ''They're a right-leaning interest group with an agenda, which apparently includes causing trouble for the Democratic National Convention."

The institute multiplied the number of delegates and other visitors expected to come to Boston by the average daily spending by Boston conventioneers in several categories. About 35,000 people are expected for the convention, 5,000 of them delegates and about 30,000 of them news media and other attendees.

Using data published by the Greater Boston Convention & Visitors Bureau, the institute estimated that each delegate would spend $342 a day during the convention, while each nondelegate would spend $285.

Based on that, the institute calculated $48.5 million in direct spending over about six days -- the average time conventioneers stayed at the last Democratic convention.

It then added the $39.5 million in cash and in-kind contributions received by the Boston 2004 host committee and $25 million in federal security funds the city received, to arrive at $113 million in new spending in the city.

The institute then used software to calculate the ripple effect of that spending on the local economy to arrive at its $122 million figure.

John Barrett, director of research at Beacon Hill Institute and principal author of the study, said he could not be sure about what accounts for the disparity between his estimate and the convention organizers'. But his study included only dollars likely to ''stick" to Boston's economy and not be taken elsewhere after the convention, and that may account for the difference, he said.

''If a delegate goes to buy a T-shirt from a local shop owner for $10 and that shirt is made in China, only about $3 stays with that shop owner," Barrett said. ''The rest goes to pay the people who made the shirt. That $3 is what you want you want to count."

McQuilken, though, attacked Barrett's methodology, arguing that political delegates spend more money over a broader area than other conventioneers.

''This analysis looks at other types of conventions, and what it fails to do is compare this convention to other political conventions," he said.

The $150 million estimate ''is based on a direct comparison with past political conventions in other cities, not your average software convention," he added.

Since 2001, when Mayor Thomas M. Menino appointed a committee to chase the Democratic and Republican nominating conventions, city officials have been using the $150 million figure to promote the benefits of hosting the high-profile gatherings. The city dangled $20 million in cash contributions from the private sector to help land the convention.

Veterans of past efforts to win national political conventions said the disparity between the two estimates could hurt the city's credibility with business leaders. If the convention doesn't live up to the city's billing, executives might be reluctant to donate to similar efforts in the future, said Jack Kyser, chief economist at the Los Angeles County Economic Development Corp. Los Angeles hosted the 2000 Democratic National Convention, which pumped $147.1 million into that city's economy, according to official data.

''The reason why you are donating to the effort is you see some benefit to your firm and you see some benefit to the community as a whole," Kyser said. ''If you don't get the benefit you thought you were going to get, the next time the city comes calling you're going to be skeptical."

Karen Grant, a spokeswoman for Boston 2004, disagreed.

''We have had unprecedented support from the community at large, including businesses, nonprofits, and individuals," she said. ''People participate because it gives them an opportunity to show their civic pride."

Regardless of whether the actual number is closer to $150 million or $122 million, Barrett said, the convention will still be well worth the city's effort.

''It's new wages and profits, taxes that are collected," he said. ''It's a contribution to people's incomes."

Keith Reed can be reached at reed@globe.com.