Note. The variance in liability to personality at each assessment is parsed into that which is due to additive genetic effects (A1, A2, and A3), shared environmental effects, and non-shared environmental effects (E1, E2, and E3). Though used in the model, shared environmental effects (C) are not represented herein for ease of presentation. Similarly, this path diagram represents only one twin in a pair (results are identical for the co-twin). Paths, which are squared to estimate the proportion of variance accounted for, are represented by lowercase letters followed by two numerals (e.g., a11). Genetic and environmental correlations are indicated by a lowercase r, followed by information regarding the specific correlation in question (e.g., rA17→24 Indicates the genetic correlation between ages 17 and 24).