Slightly more than one third of taxpayers itemize (more than half of married taxpayers and a little less than a quarter of single filers).

Four-fifths of taxpayers who itemize have the mortgage interest deduction (only 6% points) and seven-eights deduct property taxes. Almost everybody deducts state and local income taxes. Four-fifths deduct charitable contributions, almost half deduct tax preparation fees, one-third deduct unreimbursed employee business expenses, one-fifth deduct medical and dental expenses, and one-fifth have miscellaneous deductions. Less than 5% deduct investment interest, gambling or casualty losses.

But the usual triggers for itemization are mortgage interest and real estate taxes, which together almost half of the dollar value of itemized deductions. They are followed by state and local taxes (about a fifth), charitable contributions (about a seventh) and miscellaneous deductions (almost a tenth). So if you own a home, are wealthy or generous, you should consider whether itemizing will yield more of a tax benefit than the standardized deduction.