From Arnold Kling’s summary of PopTech! [found via JOHO]

“Longevity has been increasing fairly rapidly for the past hundred years, from about 45 years at the beginning of the 20th century to close to 77 years at the beginning of the 21st. However, if we reach the point where longevity increases at a rate greater than one year per year, then from that point on people will live forever.”