A poor yield on single premium endowment

My wife's single premium endowment will mature in 2 months time. She will get a yield of 3.06% for the past 5 years.

During the past 10 years, the insurance company reported that the averge yield was 7.8%. I found the yield of 3.06% to be unsatisfactory, for a participating policy.

Here are some key figures:

Single premium $50,000
Insurance company earned 7.8% for 5 years, giving a total of $72,800
Maturity benefit: $58,100

By giving a low payout of $58,100, the insurance company kept $14,700 for the 5 years, or $2,940 a year. That is a lot of money to keep from the policyholder for the small insurance protection provided by this policy. The actual expenses for this policy are quite low anyway.

If the insurance company had earned a low return, they would have reduced the payout (i.e. cut the annual and special bonus). As the insurance company had actually earned a high return, they should increase the payout to the policyholder on the maturity, instead of keeping a large part of the unexpected gain in the fund. This is the "promise" of a participating policy.

I have raised this matter with the insurance company. I believe that they payout has not meet the standard of "fair and consistent with the actual experience".