Principal Financial Group Inc. reported operating earnings of $134.8 million for the third quarter, a 30 percent decline from the $193.2 million it reported a year ago. Operating earnings were negatively affected by an adjustment known as a periodic actuarial assumption review, which resulted in a $90.7 million non-cash charge to earnings. Without this adjustment, operating earnings would have been up 8 percent, the company said. Principal reported record assets under management of $392.2 billion, up 22 percent compared with the year-ago quarter, and strong retirement investment sales of more than $7.6 billion for the quarter.