In the above note I suggested that the improved accuracy of E.L.T. No. 13 as compared with E.L.T. No. 12 was largely because E.L.T. No. 13 was based on census and death registrations at which the date of birth had been asked for instead of age. Since writing that note I have come across interesting evidence that more accurate results are obtained when date of birth is asked for at a census than when age is required.