Stern goes on:
The Commission should examine our country's entire retirement security system, private and public. Taxpayer dollars are spent in a multitude of ways, not just on Social Security with the aim of promoting retirement security. Yet, many Americans retire with anything but security. We should include as part of our agenda ideas for strengthening the private parts of the retirement security system, reviewing both adequacy and solvency of the Social Security system, and the possibility of add-on universal private accounts.
Emphasis in the original. Additionally, Stern says the commission should examine the impact comprehensive immigration reform would have on the country's fiscal future, presuming that it could "increase revenues by reducing tax evasion by employers using the underground non tax economy."
You can read the entire letter here.