The DB pension without a doubt is the best retirement income that can be offered to employees, except that the purchasing power varies with inflation in the averaging years. The federal government sets an example. The pension is based on the average salary over 5 years. The salaries in the 5 years are added together and divided by 5. However there are 6 different dollars involved. There is the year of retirement say late 2015$s plus 2014$s plus 2013$s, plus 2012$s plus 2011$s. Then the pension is paid in 2016$s. 

The dollars should be converted to 2016$s since those are the dollars to be received. Then averaged.

The proof that something is wrong is in the result. For 30 years employment, the pensioners receive a 60% pension – 60% of that averaged salary. However the purchasing power, because of inflation, varies between about 57% for this year`s retiree to 44% for a 1981 retiree, reflecting the high inflation late 70s, early 80s.

Otherwise DB is an excellent pension.