naires are expressed in standard deviation units of young adults to provide a common scale for all variables. Use of this group as the reference distribution allows comparison levels of adults of different ages entering the workforce. Although young adults are only a subset of the total sample (and hence the estimate of the standard deviation from this subset may not be as precise as when the entire sample is used as the reference group), young adults may offer a more meaningful comparison when there are large age effects on the variable of interest because some of this variability will be due to effects of age. As is apparent in Figure 5-1, occupational well-being increases slightly across a 40-year age range, but the total effect is small, corresponding to less than .5 standard deviations of the reference distribution of young adults.
In contrast to the small and generally positive effects of age on variables related to personality or adjustment, age-related effects on many measures of cognitive functioning are large and negative. Figures 5-2 and 5-3 illustrate age trends in several cognitive variables from nationally representative samples used to establish norms from recent standardized cognitive test batteries (i.e., Wechsler, 1997a,b; Woodcock, McGrew, and Mather, 2001).