The United States Postal Service (USPS), on Monday, reported a net loss of $586 million this spring, a major improvement compared to the $2 billion net loss USPS experienced during the same period last year.

USPS officials stated the loss was mitigated mostly because of interest rates, associated with workers' compensation expenses, which allegedly swung in the agency's favor. Operating expenses outside the Postal Service's jurisdiction dropped by $1.6 billion during the same period last year to $389 million this spring, according to the AP.

Shipping and package revenue and volume increased by 10.6 percent and 13.4 percent, respectively, from the same quarter last year.

"The continued growth of our shipping and package services is a direct result of the Postal Service's continued efforts to offer consumers more choice, excellent value and reliable service in a growing and competitive marketplace," said Postmaster General and Chief Executive Officer Megan Brennan, according to a USPS press release. "We are investing in our network and continually enhancing our services to best compete for America's shipping and package delivery business."

The Postal Service has been focusing its efforts on shipping as its traditional first-class and standard mail services continue to decline. In the latest quarter, revenue from first-class and standard mail went down about 2.3 percent and 2 percent, respectively, according to the Wall Street Journal.

Monday, Brennan revealed the decline in first-class mail puts "tremendous financial pressure" on the agency. Total mail volume fell by about 1.9 percent to 36.8 billion pieces of mail. However, the volume decline was mitigated by a May 31 price hike for certain mail classes. As a result, USPS' operating revenue of about $16.5 billion for the quarter was level with last year.

Frederic Rolando, president of the National Association of Letter Carriers, said the results represent an impressive "turnaround continuing in full force." The group cites the $1.2 billion in "controllable" net income for the first three quarters of the year. Controllable income excludes certain factors such as the requirement that the USPS prefund retiree health benefits.

The operating losses during the third quarter aren't unusual, and "it doesn't change the fact that 2015 is turning into one of the USPS' most impressive annual performances since the Great Recession," he said in a statement.