When The Post dug into the backlog for disability benefits at the Social Security Administration a year ago, it discovered that the line was approaching one million applications long. The number of people in this queue was so large that it exceeded the population of six different states.

Since then, the line has only gotten longer, according to a new report by the agency’s watchdog.

The average time to process the claims — which have now reached the one million mark — is up to 450 days, Inspector General Patrick O’Carroll Jr. wrote in late September, calling the number of pending cases the largest in Social Security’s history.

Social Security pays out disability benefits to people who can’t work because of mental or physical ailments. The backed-up part of the system handles appeals from applicants who’ve been turned down because they were not disabled enough. The appeals go through an administrative law judge, who holds a hearing.

The Post wrote in October 2014 that the Office of Disability Adjudication and Review, which does the hearings and appeals, was 990,000 cases behind. The wait for someone to hear whether their appeal would be approved or denied was 435 days on average. As of March, the average wait jumped by 15 days, the inspector general found.

The backlog in May of 2007, when Social Security announced its first big plan to move the bureaucracy faster, was 743,800 cases. “Even with the implementation of numerous backlog initiatives since 2007, SSA’s pending hearings backlog had increased significantly, and the [average processing time]” had gotten worse, auditors concluded.

Their report, released late last month, found four lingering reasons: The number of requests for hearings has increased, the federal judges who hear appeals have become less productive, there are fewer attorneys on staff who could decide cases without going through the lengthy hearing process and fewer judges overall.

The backlog has come under scrutiny not just from the inspector general and the Government Accountability Office, but from Congress, which has held numerous hearings on the issue. In July, Social Security replaced the two officials in charge of the appeals office, shifting them to other jobs at the agency in favor of new leadership to tackle the backlog.

Three months later, the new head of the office says she is “putting the finishing touches” on a plan to reduce the number of pending cases and speed the system up.

Terrie Gruber said in an interview that her goal is “compassionate and responsive” service to applicants for disability benefits, who, if they are approved, get an average monthly benefit of $1,145, or $13,740 annually.

“We’re committed to new ways of doing business,” she said.

One of the biggest changes will include better triage of cases, so many don’t ever get to a lengthy hearing before a judge. New, electronically-generated data has helped the agency determine which appeals could be screened by attorneys and federal claims examiners, who can make decisions themselves, faster than judges, Gruber said. The number of attorneys is being increased.

When cases do go before judges, a new initiative is assigning support staff to arrange the files in better order, getting rid of duplicate medical documents and evidence that take a long time for judges to sort through.

A primary goal is hiring more judges, Gruber said, about 1,800 to 1,900 by fiscal 2018, an increase of about 400. Also, she is making use of new technology to enhance the quality of video hearings in remote locations where there are no judges, and improving support staff’s communications with judges when video hearings are involved.

A new pilot program is creating “pre-hearing” conferences at a handful of  local Social Security offices, so applicants who don’t have attorneys can know what to expect when a judge hears their case.

Even with these changes, Gruber says her goal is to get to a 270-day wait by fiscal 2020, which she defines as eliminating the backlog. “Half of the million pending cases are a true backlog,” she said. “There will always be some level of pending cases.”

The inspector general’s office plans to audit the new initiatives and report on them in 2017. But as late as last month, auditors criticized Social Security officials for not making public a “long-term, multi-year strategy that specifically addressed the growing pending hearings backlog and worsening timeliness.”