The proportion of pensioners to working age people in Calderdale will rise in the coming years, according to new figures.
Economic experts say higher taxes or lower spending will be needed to cope with the cost of the UK's ageing population.
By 2026 there’ll be 316 people of state pension age for every 1,000 still working.
The ratio, produced by the Office for National Statistics, takes into account migration from overseas and other parts of the UK, based on trends for the past 10 years.
Previous projections show the current rate is 297.
Most of the lowest ratios are in London boroughs with growing young populations. The lowest ratio in England in 2026 will be 91 in Tower Hamlets. The highest will be 679 in West Somerset.
The new figures take account of the gradual increase in the retirement age introduced by the Government. By 2026 it will reach 67.
David Sturrock, research economist at the Institute for Fiscal Studies, said the ratio provided a useful measure for the pressure an ageing population will place on society.
He said: "We think there needs to be some response to demographic pressures, either through spending reduction, tax rises, or some combination of both.
"Some steps have been made, such as raising the state pension age, but on current trends the ageing population will continue to grow, and it will demand action from politicians."
According to the main population projections done by the ONS there are currently 38,889 people of pension age in Calderdale and 130,810 of working age.
Caroline Abrahams, Charity Director at Age UK, said: "Many will be surprised by how much older people contribute to society including a great deal of knowledge, skill and energy. Whether they are volunteers, informal carers or paid employees, many are redefining what it means to be ‘an older person'.
And she warned: "Our creaking social care system has been chronically underfunded for years and will simply not be able to cope with the extra demand that an ageing population will bring unless substantial funding is found.
“We also need to create age friendly communities that offer a good quality of life across the generations, by designing environments that are safe and pleasant to live in, with good local facilities and open spaces.
"If we can get this right it will help to sustain the health, well-being and quality of life for everyone, regardless of age.”