Evolution of the main indicators of Spain’s educational system from 1940 to 1974.

<p>(A) Educational attainment in Spain by year of birth. (B) Mean years of schooling by sex and year of birth for cohorts at 19 and 24 years old. Data source: <i>Historical Statistics of Spain</i>. <i>19</i>^<i>th</i><i>and 20</i>^<i>th</i><i>Centuries</i>. Fundación BBVA [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0143796#pone.0143796.ref023" target="_blank">23</a>]</p

Proportions of variance explained (95% CI), by sex and cohort.

<p>Proportions of variance explained (95% CI), by sex and cohort.</p

Unstandardized estimates of variance explained by additive genetic influences (A), common environment (C) and unique environment (E) with 95% Confidence Interval, by sex and cohort.

<p>Unstandardized estimates of variance explained by additive genetic influences (A), common environment (C) and unique environment (E) with 95% Confidence Interval, by sex and cohort.</p

Path diagram for the basic univariate twin model used estimation of sources of variance in EA.

<p>The additive genetic factors (A) have a correlation of 1 between MZ twins and 0.5 between DZ twins, respectively. Shared family environment (C) is correlated 1 for both MZ and DZ twins. Unique environment (E) is the source of variance that will result in differences among members of one family and is, thus, uncorrelated between members of MZ and DZ pairs. The regression coefficients for A, C and E effects, are ‘a’, ‘c’ and ‘e’, respectively.</p

Distribution of completed educational levels by sex and cohort.

<p><i>n</i>: number of observations.</p><p>Distribution of completed educational levels by sex and cohort.</p

Polychoric twin correlations with 95% Confidence Interval (CI) by zygosity, sex, and cohort.

<p><i>n</i>: number of observations;</p><p>MZM: monozygotic male pairs;</p><p>DZM: dizygotic male pairs;</p><p>MZF: monozygotic female pairs;</p><p>DZF: dizygotic female pairs;</p><p>DZO: dizygotic opposite sex pairs.</p><p>Polychoric twin correlations with 95% Confidence Interval (CI) by zygosity, sex, and cohort.</p

Baseline characteristics of participants for ‘myocardial infarction’ lifetime and in the last two years.

<p>Baseline characteristics of participants for ‘myocardial infarction’ lifetime and in the last two years.</p

Odds ratios and 95% CIs from multivariate models for the relationship between chronic LBP and myocardial infarction—last 2 years.

<p>Odds ratios and 95% CIs from multivariate models for the relationship between chronic LBP and myocardial infarction—last 2 years.</p

Total sample analysis and co-twin control analyses for other coronary heart diseases lifetime and in the last 2 years.

<p>Total sample analysis and co-twin control analyses for other coronary heart diseases lifetime and in the last 2 years.</p

Baseline characteristics of participants for ‘other coronary heart diseases’ lifetime and in the last two years.

<p>Baseline characteristics of participants for ‘other coronary heart diseases’ lifetime and in the last two years.</p