The company announced that the total payout on a 25-year endowment with premiums of pounds 50 a month would be pounds 115,554, almost pounds 2,700 higher than the amount paid out this time last year, equal to a net annual yield of 13.9 per cent.
Payouts on maturing 15-year policies will also rise slightly, adding pounds 348 to the pounds 23,972 achieved last year.
However, General Accident said a10-year policy would pay pounds 119 less this year, at pounds 10,289, than in 1996. Returns on a 20-year term dropped even more substantially over the past 12 months, from pounds 58,044 to pounds 54,914.
Peter Hales, assistant general manager at General Accident, said that the lower maturity value of a 20-year policy was explained by the company's decision to base its payouts on returns achieved during its lifetime.
"With 20-year terms, what we are seeing is the effect of the rise in the stock market in 1975, just after the crash a year earlier, disappearing from policies that were taken shortly after that time," Mr Hales said.
He pointed out that returns on a with-profits pension policy taken out 20 years ago were equivalent a gross yield of 15.4 per cent a year.
With-profits policies have annual bonuses attached to them plus a large final maturity. The aim is to smooth returns over longer periods.
Millions of endowments were sold in the 1980s alongside interest-only mortgages. In recent years, doubts have been raised over whether maturing policies will pay out.
But Mr Hales added: "We are confident that the returns on our policies, not just 25-year or 20-year with-profits endowments, but over 10 and 15 years too, will be enough to ensure mortgages are paid off in full when they mature."
General Accident's returns, which opened the beginning of the annual bonus season, come as Friends Provident, a smaller life insurer tipped as a takeover target, announced that it is cutting payouts on all bar its 25-year policies.
On monthly premiums of pounds 50, as before, Friends Provident will pay out pounds 60 more, at pounds 103,719, than last year. But for 20-year endowments, the payout fell again to pounds 52,688, a decline of pounds 1,400 compared to 1996. Over 10 years, payouts were more than 3 per cent lower at pounds 9,786.
Michael Doerr, group chief executive at Friends Provident, said the annual returns achieved by the company were 9.5 per cent over 10 years.
This compared well with an average inflation rate of 4.5 a year over the past 10 years and returns of 2 per cent for a typical building society share account over the same period.Reuse content