Under current California law, a homeowner in Santa Monica could end up paying 17 times more in property taxes than his or her immediate neighbor with comparable property.

That's due to the effects of the tax slashing initiative called Proposition 13 passed in 1978.

With the Supreme Court scheduled to test the constitutionality of the measure Feb. 23, Riverside Press Enterprise reporter Bob LaBarre decided to take a look at exactly how the alleged tax disparities stack up.

In a two part series LaBarre revealed that Prop. 13, originally designed to prevent modest homeowners from losing their houses, was producing huge differences in property taxes.

Only those homeowners who bought their houses before the end of 1975 fully benefit from the measure.

And those who bought their homes since 1975 claim the inequities are a violation of the equal protection clause of the 14th Amendment of the Constitution.

LaBarre expected the usual problems in obtaining a database for his story.

But when he went to the Riverside Assessor's office he found the staff was more than cooperative. They were so intrigued by the problem he presented they actually did the work for him.

"One of the things I learned was, 'ask the nerds,'" said LaBarre. "The systems people became so fascinated by the questions that they agreed to help me create the data base."

Just 24 hours later LaBarre had the average tax paid by homeowners broken down by the last year its value was assessed.

Under Prop. 13 a home's value is not assessed unless it is sold. The flat rate for property taxes is one percent of the assessed value and it can be increased two percent per year.

"I was kind of disapointed, because it was so easy," said LaBarre about his first experience at computer sleuthing since finishing a MICAR seminar October.

However, LaBarre realized that the average figure he was using might be inaccurate because older houses would naturally have a lower value, and thus a lower tax assesment.

"It was so easy that I thought that maybe the houses were not comparable, so I did the same thing for all the houses that sold in 1990," said LeBarre. "What we did was we took from the assessors roll all the properties that had to be updated. It turned out there were 24,000 properties that had been sold."

LeBarre took all the residential properties and broke them down by base year before they were sold. He then totalled up the assessment on the 1975 properties right before their sale and right after.

"That revealed that 1975 properties, when sold in 1990, were assessed at 21 percent of their market value," LeBarre explained. "But 1990 properties were assessed at 85 percent of their market value."

LeBarre then pulled out specific houses on individual streets in Palm Springs, Riverside and her show the effects of Prop. 13.

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