A proposed penny sales tax increase would cost medium-income Oklahomans about $262 a year and raise $608 million annually to finance public schools and higher education, a new data analysis shows.

The bottom 20 percent of Oklahoman households would chip in $90 a year, the top 1 percent would pay $1,691, the study says.

As a percentage of income, though, the tax would fall hardest on the poor. That's because they spend a bigger portion of their income on retail purchases.

The analysis was prepared in recent days by the Institute on Taxation and Economic Policy, a Washington, D.C., research organization. It was requested by the Oklahoma Policy Institute, a Tulsa-based group that supports higher levels of funding for education and other core state services.