Random graphs (38): Line graph with two y-axes

import excel "Figure 3.xlsx", sheet("Figure 3") cellrange(A3:E118) firstrow case(lower) clear

rename anne year
rename agemoyenlamaternitfrance afb
rename tauxdegmellitfrance twin

label var year "Year"
label var afb  "Mean age at childbearing"
label var twin "Twin deliveries per 1,000 deliveries"
    
twoway (line afb year) ///
       (line twin year, yaxis(2)) ///
      , xlabel(1900 1925 1950 1975 2000 2013) ///       
        xtitle("Year") ylabel(, format(%6.0f) axis(2)) ///
        legend(pos(7) ring(0)) ytitle("Age in years") ///       
        ytitle("Twin deliveries per 1,000 deliveries", axis(2)) ///
        caption("{it:Source:} Pison {it:et al.} (2004), {it:Population}, doi: 10.2307/3654895", span)