Based on the path coefficients in Table 3, standardized variance components were estimated and appear in Table 4. The proportion of total variance in CU attributable to additive genetic effects was steady at 32% to 33% between 15 to 21 years but then increased to 54% between 22 to 25 years. By contrast, the proportion of shared environmental variance over the same period declined from 45% to 16%. Although the standardized additive genetic and shared environmental variance in PGD appeared stable over time, the proportion of additive genetic variance explained by CU increased; it ranged from 50% to 58% between 15 to 21 years and 78% between 22 to 25 years. This coincided with a decline in the proportion of shared environmental variance explained by CU which equaled 73% between 15 to 17 years and 25% by 22 to 25 years. Most of the non-shared environmental variance (74% to 79%) in PGD was unique and not attributable to CU.
