A report from the Internal Revenue Service found that a small minority of nonprofit hospitals provide the bulk of uncompensated care for the poor. The IRS also found that the top executives at a group of 20 hospitals it examined more closely earned an average of $1.4 million a year. At least one of the 20 hospitals was compensating its top executive excessively, the agency said. The findings rekindle concerns about the tax-exempt industry at a time when government aid to corporations is drawing fire. The IRS declined to name any of the hospitals in the report.