President Carter's new tax-cut proposals would leave a significant number of Americans paying a bigger slice of their income in federal taxes next year than they paid in 1977, according to a new analysis.
The larger tax bite would effect two groups: single persons who earned less than $3,300 - or more than $4,500 - in 1977, and four-person families with incomes of less than $8,000 or more than $23,000.
The estimates, compiled by National Journal, the weekly government affairs magazine, conflict somewhat with those provided by the Carter administration, which showed proportionally more taxpayers enjoying tax relief.
The difference is in the allowance made for inflation. The Journal's compilation assumed that tax-payers' wages would be rising to keep pace with living costs this year and next. By contrast, the administration used the same income levels for both 1977 and 1979.
The difference often is significant. For example, when expected wage increases are counted in, a family that earned $15,000 in 1977 would seee its income rise to $17,181 in 1979 - enough to increase its tax bill.
When federal income taxes and Social Security payroll taxes are counted, together, taxpayers in the two groups affected could end up paying as much as 2 percentage points more of their income in taxes, even if Carter's bill passes.
For example, a single person who earned $15,000 in 1977 paid 20 percent of his or her earnings in combined income and payroll taxes. By 1979, that person wouldd be making $17,181. Even under the Carter proposal, he or she would be paying 20.9 percent.
A four-person family earning $6,000 last year paid 2.5 percent of its income in taxes. By 1979, that family would be earning $6,872. Under Carter's tax plan, it would be paying 4.5 percent of its income in taxes.
Families earning $23,000 or more also would suffer under Carter's proposal.
The National Journal's calculations were not disputed by the Treasury. Emil M. Sunley, deputy assistant secretary of the treasury for tax policy, confirmed that the thrust of the compilations was "correct."
Sunley noted by way of defense that single tax-payers received "a disproportionately high" tax cut in 1976 when they were allowed to take advantage of the $180 a person credit, and have enjoyed substantial tax relief since.
He also pointed out that the Journal's calculations for families with incomes of less than $8,000 a year do not take into account Carter's proposal to expand the earned income credit for the poor.
However, Carter's plan would not liberalize the earned income credit until 1980 or 1981. So families with earnings below the $8,000 level still would suffer a bigger tax bite in 1979.
Sunley said the administration intended only that the tax cuts offset inflation and payroll tax increases for the economy as a whole. "They weren't intended to do so on a taxpayer-by-taxpayer basis," he asserted.
A spokesman for the Journalsaid its calculations were not intended to imply that the administration had misled the public in its earlier es timates. "It'h just that they should have included this as well," he said.