In your article 'How living longer is putting millions at risk of poverty' (9 May) you state that ONS life expectancy figures do not 'take account for changes in mortality over time'. This is not the case - although 'period life expectancy' is calculated this way, ONS also produces 'Cohort life expectancy' which does in fact take account of assumed improvements in mortality over time.

Readers can use our life expectancy calculator, based on cohort life expectancy, to produce an estimate of how long their pension might need to last, here:

Yours faithfully,

Emma Rourke
Director, Public Policy Analysis
Office for National Statistics
Segensworth Road
PO15 5RR