The older people become, the younger they feel and the more likely they are to see “old age” as a time occurring later in life, according to a national survey on aging released on Monday.

Currently, about 40 million Americans, or one in eight, are 65 and older. By 2050, one in five American will be in that age group. The center surveyed about 3,000 adults 18 and older via land and cellular telephone lines in February and March of this year.

The survey found not just a gap between actual age and the age people say they feel, but also that the gap between reality and perception increases with age.

On average, survey respondents said old age begins at 68. But few people over 65 agreed; they said old age begins at 75.

Respondents under 30 said 60 marks the beginning of old age.

“Old age is always a bit older than you are,” said Jeffrey Love, research director at AARP.