After Councilmember Mike Healy announced Monday that a poll he commissioned showed almost 70 percent of city voters would support a half-cent sales tax increase for eight years to fund general services, community members and Mayor David Glass challenged the validity of the poll results and the effects an additional tax would have on other November ballot taxes.
Healy said that a professional polling firm performed the poll, but would not disclose which firm. He said the Petaluma Lodging Coalition and the Petaluma Police Officers Association covered the $2,000 survey cost jointly. While typical professional polls usually consist of live polltakers conducting 20 to 30 minute interviews with subjects and cost closer to $20,000, the poll Healy conducted is called a "Robocall" poll and features a two-minute automated message complete with touchtone responses.
Healy said that because there is almost no paid labor involved, it shrinks the cost of the survey dramatically and allows for a much larger sample size.
"Typically, you get 400 responses to polls with a 4.9 percent margin of error," he said. "We placed 20,000 calls and got 1,216 responses, which shrinks the margin of error to 2.2 percent."
But local media consultant and former Councilmember Brian Sobel said that while he has no knowledge of Healy's particular poll, "Robocall" polls are generally considered the least reliable scientific polls available.
"The rule of thumb is the longer the poll, the more accurate the results," he said. "The accuracy of the poll is really based on the quality of the questions and whether the respondents are who you think they are and not someone else in the target's household answering the phone."
Sobel added that the size of the sample polled does little to affect the accuracy of a poll and that just because someone is able to poll a large sample size doesn't mean that the results are as accurate as they could be.
"The poll's accuracy isn't based on whether you get a response," he said. "It's just hard to say that a poll with one or two questions is effective because you haven't taken the time to build the arguments for and against it to the voter being polled."
Healy said the automated poll conducted this week informed participants that local officials are considering a sales tax measure for the November ballot to help maintain essential city services, such as police and fire protection, drug and gang-crime prevention, school resource officer restoration, street repair and stormwater maintenance.
It then asked voters how supportive they would be of a half-cent sales tax increase for eight years, with all revenue staying in the city to be used at the city's discretion. Those polled could say they were very supportive, somewhat supportive, not very supportive or not supportive at all. Healy said 47 percent of participants responded as very supportive, 21 percent said somewhat supportive, 11 percent said not very supportive and 17 percent were not supportive at all. 5 percent had no opinion in the matter.