The taxpayers of Tisbury have been warned they will have to come up with some $1.5 million each year for the next 30 years to meet their currently-unfunded liabilites to town employees.

The huge figure is contained in a comprehensive analysis, carried out by Jon Snyder of the town’s finance and advisory committee, of the problem posed by the failure of Tisbury — and other Martha’s Vineyard towns and regional entities — to provide for health insurance and other post-retirement benefits.

Mr. Snyder estimates the current liability for Tisbury at some $19.5 million, and the total liability for all Island towns and major regional entities at more than $89 million.

For Tisbury residents, meeting the cost would mean large property tax increases — $302 per year on a $500,000 home.

Mr. Snyder’s analysis, entitled Wrestling the Alligator, says that while the town has been funding its pension plan, provision for other promised benefits, particularly health benefits, has not been made.

“These future benefits have become a huge, scary 20-foot alligator,” he says in the document.

Tisbury faces the biggest liability of any public entity on the Island, but Mr. Snyder’s report notes most other towns in Massachusetts, indeed, across the country are probably in a similar situation.

On-Island, he calculates the unfunded liabilities are $19.52 million for Tisbury, $14.51 million for Edgartown, $10.82 million for Oak Blufffs, $3.56 million for West Tisbury, $2.97 million for Chilmark and $1.91 million for Aquinnah.

Among other public entities, the largest unfunded liabilities include the regional high school district ($16.15 million), the county ($5.57 million), and the up-island regional school district ($6.63 million).

All told, Mr. Snyder calculates a public unfunded liability for the Island of some $89 million. His figures are, for reasons he explains in his report, about one-third higher than those calculated by a consulting firm, Buck Consulting, brought in to run the numbers about 18 months ago.

To date, Mr. Snyder’s analysis says, “Tisbury has been paying retirees’ health insurance every year on a pay-as-you-go basis: as each year’s insurance premium bill comes in, the town pays it. Tisbury is now paying $582,000 a year for these pay-as-you-go retirees and their families.”

That cost is expected to increase rapidly. Using actuarial projections, Mr. Snyder — a financial planner who describes himself as “over-educated in finance and statistics” — estimates the health insurance cost in 2020 to be about $1.64 million.

And if the town continues with its current pay-as-you-go approach, he says in his report, the town would be paying over $8 million a year at the end of the 30 year period.

The sooner the problem is addressed, he notes, the less the cost in the long run, because interest would be earned on any money put aside.

The key variable in determining how much must be set aside is interest rates.

“We hired consultants to [analyze] a number of moving parts — how many people we employ, when those employees retire, the cost of benefits each year, and so on,” he says.

“The consultants tell us the present value of the benefits we have promised our employees adds up to between $13 [at 8 per cent] and $26 million [at 3.5 per cent].”

“For that (optimistically low) $13 million, if we put away $1,070,000 every year . . . when we add up all the deposits and all the interest over 30 years, we will have paid off that liability. If we take the less optimistic number of $26 million, we would need to put away $2,150,000 every year.”

Mr. Snyder based his own calculations on an annual rate of return of five per cent, making the annual payment $1,566,000.

The problem is even now that the financial ‘alligator’ has been sized up, an article on this year’s town meeting warrant seeks only an appropriation of $672,000 to begin addressing the problem.

Mr. Snyder considers it grossly inadequate and told Tuesday’s meeting of the selectmen he would push to have the warrant article amended when the finance and advisory committee met with finance director Tim McLean on Thursday night. (That meeting was underway at press time.)

He also offered to make his argument in favor of the $1.566 million payment directly to the annual town meeting.

On Wednesday, Mr. Snyder told the Gazette: “Right now, it is a $672,000 article, but I’m going to advocate the $1.566 million because on town floor you can always come down, but you can’t amend up.

“I expect the Fin Com will say we can’t do that, and I expect even then the town floor will ratchet it down. I can understand why; it’s going to scare people to death.

“[Selectman] Tristan Israel’s first suggestion was that we put $50,000 or $100,000 away. But when the unfunded liability is growing at over $350,000 a year, anything less than that won’t even stop the growth of the problem.

“As to what the number on the warrant article ultimately is — that’s up in the air right now,” Mr. Snyder said.

So, where did the figure of $672,000 now in the warrant article come from?

The consultants provided what Mr. Snyder calls an “improbably optimistic” estimate of an eight per cent return on savings. They also assumed the town’s payment would increase by 4.5 per cent each year, an escalation Mr. Snyder compares to an adjustable rate mortgage, in which payments start low and increase every year.

Even then, the figure would only pay down the liability already accumulated. Another $357,000 would be required to meet this year’s increase in future benefits earned by current employees.

Worse yet, all the numbers in the consultant’s report were two years out of date, meaning Tisbury’s unfunded liability was already at least $300,000 larger.

And, as he notes at the very end of his report, “once Tisbury addresses its own unfunded liability, the town still shares some of the regional entities’ unfunded liabilities.”

Mr. Snyder told the selectmen on Tuesday, and told the Gazette again on Wednesday, that he did not expect to make any friends by pointing out the necessity of facing up to the problem.

“I’m taking the pure, hard-nosed finance approach that says it’s prudent to do it now. It will hurt, but it will hurt more if you don’t,” he said.

And, he suggested, it might ultimately benefit the town by improving its credit rating, resulting in lower costs for future bond issues.

“But fundamentally,” he said, “it’s an issue of fairness. We are putting off costs until tomorrow while enjoying the benefits of these employees’ work today. We are pushing the expense off onto future citizens.”