WASHINGTON (Reuters) - The U.S. retirement system does not need a major overhaul or private accounts and can be stabilized through a series of smaller fixes, the nation's largest lobby group for the elderly said on Wednesday. The AARP, formerly known as the American Association for Retired Persons, said the amount of wages that can be taxed for Social Security (news - web sites) should be raised from $90,000 to $140,000. The change could be phased in over about 10 years and would cut the projected shortfall by 43 percent. The government should also diversify investments for the fund that...