"Over the years AARP has become much more than an advocacy and service organization for older Americans. It receives more than $150 million each year in commissions on insurance, mutual funds and prescription drugs sold to its members." From Krugman's article.
It isn't "over the years", it's ALWAYS been that way:
Dr. Ethel Percy Andrus, a retired high school principal, founded AARP in 1958. AARP evolved from the National Retired Teachers Association (NRTA), which Dr. Andrus had established in 1947 to promote her philosophy of productive aging, and in response to the need of retired teachers for health insurance. At that time, private health insurance was virtually unavailable to older Americans; in fact, it was not until 1965 that the government enacted Medicare, which provides health benefits to persons over age 65. Dr. Andrus approached dozens of insurance companies until she found one willing to take the risk of insuring older persons. She then developed other benefits and programs, including a discount mail order pharmacy service. Over the years NRTA heard from thousands of others who wanted to know how they could obtain insurance and other NRTA benefits without being retired teachers. After ten years, Dr. Andrus realized the time had come to create a new organization open to all Americans. Today, NRTA is a division within AARP.
At a time when older persons could not obtain life, health, or automobile insurance easily, Mr. Davis found innovative approaches to solving this problem. In 1963, he founded the Colonial Penn Group, Inc., a major insurance company, which offered unprecedented health and auto insurance for the elderly. This became a model for subsequent plans throughout the insurance industry. While serving older Americans, his professional career flourished and his company became one of the nation's leading insurers.
http://www.aarp.org/leadership/Articles/a2003-01-13-aarphistory.htmlAs a friend and colleague of Dr. Ethel Percy Andrus, Mr. Davis was closely involved in establishing the American Association of Retired Persons (AARP), and later served as its Honorary President. Mr. Davis's commitment to the cause of older Americans brought him to testify before Congressional committees on issues related to aging and he was a delegate to the 1970 White House Conference on Aging. Mr. Davis and Mrs. Andrus were closely involved in the legislation of Medicare by Congress.
http://www.upenn.edu/ldi/davis.html