(Mike Blake/Reuters)

This post has been updated

After years of cost-cutting to adjust to steep financial losses, the U.S. Postal Service is contending with angry customers whose mail is taking longer — sometimes much longer — to arrive.

New research by Congress’ watchdog now says that the post office’s tracking system for measuring on-time delivery is so unreliable that there’s no way to know how late the mail really is.

[As late mail soars, Postal Service can’t even meet its lower standards]

In an unusually stern report, the Government Accountability Office found the Postal Service’s tracking of delivery times “far from complete” and called on the agency to provide “quality delivery performance information.”

Just 55 percent of the mail is even measured by postal officials, auditors found, making it unlikely that the agency is meeting its legal obligation to provide quality service to every corner of the United States.

Current information on performance “is not sufficiently transparent or readily available,” GAO found.

[In rural North Dakota, mail service is spotty]

“Quality delivery performance information is needed … for postal stakeholders and the general public … to assess the balance between USPS cost-cutting to address its poor financial situation while maintaining affordable postal rates and providing timely, universal delivery service,” said the report, which has not been made public and was obtained by The Washington Post.

Auditors also took regulators to task for their passive approach to the problem.

And GAO criticized postal officials for failing to provide the public with data on whether they are meeting delivery standards for rural addresses compared to urban or suburban ones. Lawmakers representing rural states, who requested the GAO study, say spotty mail service is now the new normal across their districts, with cross-country and local delivery delayed by several days.

“Service across the country, particularly in rural communities, is suffering,” Sen. Tom Carper (D-Del.), the top Democrat on the Senate committee that oversees the Postal Service, said in a statement.

[It’s not just you. Letters really are taking longer to be delivered.]

“To fix these service problems, we need to figure out their root causes,” Carper said. “Unfortunately, the Government Accountability Office found the delivery performance results that the Postal Service and Postal Regulatory Commission provide do not give Congress or postal customers an accurate assessment of service.”

Carper, who requested the study with Sens. Heidi Heitkamp (D-N.D.), Jon Tester (D-Mont.) and Claire McCaskill (D-Mo.), introduced a sweeping postal bill in September that would require measurable improvements to mail delivery across the country.

The Postal Service said in a statement that it “strongly disagrees with the conclusion that our current service performance measurement is not accurate.”

“The Postal Service is strongly committed to transparency and the regular publication of our service performance results, including those in rural areas through a rural service measurement initiative,” the agency said. “We continue to work with the Congress and our regulator to develop enhanced methods for evaluating delivery performance that are already robust and accurate.”

Officials said they use a “highly reputable firm with long-standing proficiency in the design and execution of measurement systems” to sample the timeliness of mail delivery.

The Postal Service is required by law to create standards for mail delivery and to measure and report whether it meets them. Its regulator, the Postal Regulatory Commission, is supposed to tell the agency how to measure and report on mail delivery and use the information for oversight.

[Should the Postal Service be sold to save it?]

Auditors found that almost half of the mail is not included in the post office’s system of assessing delivery times because it does not have barcodes and other information that can be tracked, on when mail arrived at the local post office, for example. There is no minimum that needs to be included.

Postal officials told auditors that they are trying to improve their scanning of mail with barcodes and working with the mailing industry to get more pieces of mail into their measurement system.

First-class mail and magazines have gradually been taking longer to arrive since 2012, when Postal Service started reducing its full-time workforce  by about 40,000 employees and closed almost 141 mail-sorting plants.

But nine months ago, service took a turn for the worse when, to prepare for another round of plant closings, the agency eliminated overnight delivery for local first-class letters that used to arrive the next day. Up to half of mail traveling longer distances was given an extra day to reach its destination.

The longer delivery times became the new normal, or “service standards” in postal jargon. Mail was considered on time if it took four to five days to arrive instead of three.

But the post office has struggled all year to meet even these lower standards, prompting the agency’s inspector general to issue an urgent alert over the summer recommending that all further closures of mail-sorting plants be put on hold until service stabilizes. (This was done under pressure from Congress as well)

Inspector General Dave Williams found that the number of letters arriving late jumped by almost 50 percent since the start of the year, delays that were compounded by severe storms last winter and changes to plant operations that started when the new standards took effect. Thousands of postal workers were reassigned and shifts were changed.

GAO sharply criticized postal regulators for their silence on late mail delivery. In a 17-page letter to auditors, Robert Taub, the regulatory commission’s acting chairman, said his staff has provided adequate oversight of the issue. He said the commission is working with the Senate and the post office to resolve the challenges with reporting on rural delivery.

Taub also outlined the challenges of tracking delivery of mail to rural areas, since “there is no consensus definition of ‘rural'” and cited the  potentially significant costs associated with “extracting, compiling, or reporting these data.”

But  Commissioner Ruth Goldway disagreed, saying the commission should take a much more forceful role in ensuring whether mail is being delivered on time. “The issue of service quality is something the Postal Service needs to be held accountable for.”

Carper’s bill would restrict the Postal Service from plant and post office closings and prohibit the agency from further slowing the delivery of mail. It would add requirements for tracking performance.   It also would allow the Postal Service to find new sources of income from the sale of non-postal products.

“The reality is that rural communities, like North Dakota, are disproportionately and unfairly impacted by cuts to mail service and delivery which have harsh impacts on families and small businesses living in those regions,” Heitkamp said in a statement. She has introduced her own bill focusing on restoring service to rural areas.

“As we learned from this new GAO report, how can the Postal Service possibly improve delivery in rural communities if it doesn’t accurately track the time it takes to deliver mail to these areas?” she said. “There is no reason why we shouldn’t have access to that data.”