adjusted to output Bxy for male and female births separately. NRR needed
saved out US bxy with male and female births, two age ranges
brought down ES file to ages 10-65 only
saved out dx and Lx from HMD, for use with NRR and ex reditributing
populations
corrected US years 1969-2009
removes NA, NaN from US bxymf
added R0 series for both sexes, ES and US
removed duplicates
Das Gupta (1973) found that his two-sex interactive r* was not always
bounded
by rm and rf, then cam eup with an explanation. Try to reproduce his
method.