From a report by Social Security's Office of Inspector General (OIG) on The Social Security Administration's Human Capital Planning (footnotes omitted):
... In a May 2022 hearing on customer service, Grace Kim, SSA’s Deputy Commissioner for Operations, explained “. . . insufficient funding over multiple years to hire the level of staff needed, and higher than average attrition rates across the agency” had driven SSA to its lowest staffing levels in 25 years. SSA’s ability to hire during the year is affected by when SSA receives its funding. SSA’s final budget is not usually passed timely as appropriations for agencies are not always signed into law when the FY begins on October 1 each calendar year. Congress and the President must approve the budget or a continuing resolution (short-term legislation to keep the Government open). Otherwise, a funding lapse may result in a Government shutdown where agencies can only conduct mission-critical activities, and non-essential work like training is suspended. As a result, SSA will send guidance as to when components can hire. SSA stated it is difficult to plan and manage funding under the Federal budget process especially if there are funding lapses or continuing resolutions. Office of Operations staff explained they cannot over-hire to account for losses throughout the year.
When SSA can hire, it often hires staff in large numbers after it receives an approved budget and trains the new hires together. One Regional Commissioner noted a “steady source of income” would allow for more balanced planning and hiring all year as uncertain budgets create cycles of hiring and freezes. Other Operations subject-matter experts explained hiring staff in large numbers creates a strain on human resource support staff who need to address a large number of staff hired at one time. Also, SSA reported the timing of funding can limit SSA from strategically hiring staff during advantageous times of the year, such as recruiting before students graduate and during the times college campuses typically hold recruitment and job fairs. Not being able to strategically time when to hire staff places SSA at risk of not hiring the most qualified candidates as they may have accepted offers from other employers and are no longer seeking employment opportunities when SSA receives funding. ...