Total UK pension liabilities rose to approximately £7.6trn from 2010 to 2015, according to the latest data published by the Office for National Statistics (ONS).
This is an increase from £6.6trn at the end of 2010, when the liabilities were last estimated by the ONS.
Of the total £7.6trn, £4trn was in state pensions, £0.9trn in the unfunded public sector and £0.3trn in the Local Government Pension Scheme (LGPS). Another £2.3trn was held in occupational schemes, including £2trn in private sector defined benefit (DB) pension plans, £0.2trn in trust-based defined contribution (DC) plans, and £0.1trn in annuities. Another £302bn was in individual personal pensions, meaning that in 2015 these outstripped DC by 25%.
The ONS data on pension entitlements is calculated from data from national accounts, with the latest spanning from 2010 to 2005, and covers pensions provided by the government, pension funds and insurance companies, to provide a full picture of UK's total pension liabilities.
Commenting on the latest figures, ONS head of national accounts Darren Morgan said the figures provide "an important snapshot of the liabilities of UK pension providers at a point in time".
"While these are obviously large amounts of money, it is important to remember that the payments will be drawn over many years."
But added that the latest figures said nothing about the sustainability of the pension system in future.
The numbers "are truly mind-boggling", commented Royal London director of policy Steve Webb.
Webb said: "Today's population has built up £7.6trn in pension promises, but has only set aside about a third of that amount to pay for them. The rest will have to be financed by tomorrow's workers.
"If we are to have a meaningful debate about how we pay for an ageing population and about fairness between generations, figures like these need to be published on a regular basis and should inform policy-making," he added.
With £2.3trn held in occupational pension schemes, the UK's pension obligations in the private sector make up 124 % of the country's gross domestic product - an increase from 102% of GDP five years ago when liabilities were £1.4trn.
KAS Bank UK managing director Pat Sharman said: "Despite the industry's size, it is somewhat under developed in respect of governance, including a clear understanding of the total cost of running a pension scheme.
"The FCA and DWP are pressing ahead with plans to legislate the mandatory disclosure of costs, and conversations around the importance of transparency are getting much-needed attention, but we need to ensure that we provide the right informative tools to support trustees and ultimately the members," said Sharman.
Also commenting on the latest data, Hargreaves Lansdown senior pension analyst Nathan Long agreed the findings raised concerns around the funding, governance and the efficiency of private sector DB pension schemes, and that the "white paper expected next week will be watched with interest".
The ONS figures also showed significant regional variations in life expectancy, with the wealthiest shows to be benefiting the most from the state pension.
Commenting on the regional and local disparities in life expectancy, Aegon Pensions Director Steven Cameron commented: "Those in Knightsbridge and Belgravia can expect to live to 89 and spend almost 80 years in good health, while those in Bloomfield in Blackpool can expect to live to 68 and spend just 47 years in good health.
"The findings have big implications for how government delivers services as they show that in some parts of the country there will be greater demand for social care in later life while in others, there will be a greater requirement for medical care at younger ages and in wealthy areas, local councils will be all too aware of the potential costs that an ageing population may place on their social care budgets."
Cameron added: "We're used to seeing figures that suggest everyone is living longer, but as today's figures show, life expectancy is closely linked to where you live.
"In some ways it's perverse but when it comes to the state pension, it's often the wealthiest who benefit most, given they typically claim for the longest but it would highly contentious to vary state pension based on wealth or life expectancy predictions."
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