Final answer:
The statement by Ponnuru is true because demographic changes and an aging population create funding challenges for Social Security that cannot be solved by economic growth alone.
Step-by-step explanation:
According to Ponnuru, even if economic growth doubled, Social Security would still become insolvent if nothing is done to change the program's benefit structure. This statement is true. The insolvency issues cannot be solved by economic growth alone because the foundational structure of Social Security is a pay-as-you-go system that is affected by demographic changes. As people live longer and the population ages, with fewer workers contributing to the system and more drawing benefits, the Social Security Trust Fund is expected to face a shortfall. To address this, benefits might need to be reduced, the retirement age changed, or payroll taxes adjusted to ensure the program's sustainability.