In "The coming job bottleneck" (Workplace, Mar. 24), your discussion of the "graybeard ceiling"--as presented in Hudson Institute's forthcoming book, Workforce 2020--Work and Workers in the 21st Century--was excellent and generally to the point. We would like to clarify one statement, however. Workforce 2020 will nowhere suggest reinforcing seniors' entitlements to make retirement more attractive. On the contrary, we suggest changing Social Security to encourage seniors to work.