Social Security's trustees say beneficiaries will get the largest payment increase in years in 2018. But older Americans shouldn't get too excited — it's just 2.2 percent, or about $28 a month for the average recipient.

Trustees released the projection on Thursday, along with their annual warning about the long-term financial problems of Social Security and Medicare, the federal government's two bedrock retirement programs.

Unless Congress acts, the trust funds that support Social Security are projected to run dry in 2034, the same year as last year's projection. Medicare's trust fund for inpatient care is projected to be depleted in 2029, a year later than last year's projection.

If Congress allows either fund to run dry, millions of Americans living on fixed incomes will face steep cuts in benefits.