WASHINGTON — Taxes rise and fall from one administration to the next, but the unpopularity of the income tax system is constant.

An Ipsos Poll finds that almost six of 10 people say the system is unfair, a percentage virtually unchanged from two decades ago.

The perception of unfairness is spread fairly evenly across income groups — though their reasons may differ. More than half of those who make less than $50,000 a year said it's unfair, and more than six in 10 of those who make more than $50,000 felt that way.

In fact, unhappiness with the tax system was spread fairly evenly across income groups, age groups and education levels.

A majority of people said the middle class, the self-employed and small businesses pay too much in taxes, the poll found. And they think those with high incomes and big businesses don't pay enough.

The survey was conducted in the days before the mid-April deadline for filing income tax returns.

Some complain the income tax burden remains unfairly placed on those with high incomes — saying the top 5 percent pay an inordinate share. And some grouse about the wealthy getting too many tax breaks.

When the government held hearings almost a year ago on how to make the tax code simpler and more fair, complaints ranged from overly complicated laws to inequitable tax breaks to undue influence of lobbyists.

Dissatisfaction remains high after numerous changes in tax law since the late 1980s.

The Reagan administration led a tax overhaul two decades ago that significantly lowered tax rates and eliminated or reduced several deductions. The first President Bush abandoned his "read my lips, no new taxes pledge" in a 1990 budget deal that raised taxes.

The Clinton administration won passage in 1993 of a deficit-reduction measure that blended tax increases, budget cuts and rebates for the working poor.

And the second Bush administration pushed successfully for tax cuts that lowered the top income tax rate to 35 percent and slashed tax rates for individuals and manufacturers.

More than half in the poll, 58 percent, said middle-income families pay too much income tax. People were almost as likely, 54 percent, to say that about low-income families.

Six in 10 said high-income families were paying too little in taxes. Two decades ago, almost eight in 10 said high-income families were paying too little.

The poll of 1,005 adults was conducted April 11-13 by Ipsos, an international polling firm, and has a margin of sampling error of plus or minus 3 percentage points.