The previous chapter focused on the application of simultaneous analysis to investigate structural models of reading comprehension. Results of the simultaneous analysis of data sets from eight countries and on two occasions showed that it was consistent with the evidence to assume a general factor underlying the ability to read with comprehension at the 14-year-old level. Hence, it can be argued that reading comprehension beyond the initial stages involves a general ability that is similarly structured across cultures and across time. As a consequence, it is meaningful and of considerable interest to compare levels of reading achievement and examine the factors that contribute to differences in levels of achievement across countries and over time. The present chapter illustrates the way in which conjunct analysis can be used to test relationships within causal models in a systematic way for country-specific effects on reading comprehension. Thus, the primary purpose of the analyses presented here is to examine whether or not general relationships can be established with respect to achievement in reading on two separate occasions.