Defined benefit pension or defined contribution 401(k): this choice used to be made for you by your employer. Today fewer than 15% of private-sector workers have access to a pension. If you are lucky enough to have one, or if you are evaluating two job offers with different retirement structures, here is how to compare them honestly.
The fundamental difference
A defined benefit pension promises a specific monthly income for life, calculated by a formula. Your employer bears all the investment risk. If the pension fund earns 3% in a bad year, you still get your formula-calculated benefit. If the fund loses money, it is your employer's problem, not yours.
A defined contribution 401(k) defines what goes in, not what comes out. You contribute a percentage of your salary, your employer may match, and the accumulated balance is yours to manage and invest. When you retire, you have a balance, not a monthly income guarantee. You bear the investment risk. You also bear longevity risk: running out of money before you die.
Who wins on total value
Over a full career, a generous pension formula often outperforms a typical 401(k) match on total retirement income. A pension formula of 2% per year of service means a 30-year employee earns 60% of final salary for life. To replicate that with a 401(k) assuming a 4% withdrawal rate, you would need roughly 15 times your final salary saved. That requires substantial savings and strong investment returns over the full career.
The pension comparison only holds if you stay with the same employer for a full career. A pension with 10-year vesting that you leave after 8 years pays nothing. A 401(k) with 3-year vesting that you leave after 8 years is fully portable. For a mobile workforce, the 401(k) has a structural advantage no pension formula can overcome.
Longevity risk and the guaranteed income argument
The pension's strongest argument is longevity protection. A $3,000/month pension for life pays $36,000/year whether that is 5 years or 35. A 401(k) balance is finite. At a 4% withdrawal rate from a diversified portfolio, most financial planners say the money should last 30 years, but should is not guaranteed. The pension is.
The flip side: a pension that pays $3,000/month for life then stops (no survivor benefit) provides zero to your heirs. A $900,000 401(k) balance is an estate asset. For someone in poor health, childless, or with a surviving spouse who has strong independent income, the 401(k)'s bequeathability matters.
Inflation
Most private-sector pensions have no cost-of-living adjustment. A $3,000/month pension in 2026 is $3,000/month in 2046. At 3% annual inflation, that is worth about $1,660 in today's purchasing power 20 years from now. A 401(k) invested in assets that track economic growth at least has the potential to maintain purchasing power. The pension's fixed payment becomes less valuable every year inflation runs.
Government pensions (FERS, CSRS, state systems) typically include COLA adjustments. Private-sector pensions almost never do. If your private-sector pension has no COLA, factor the purchasing power erosion into your analysis explicitly.
PBGC protection
Private-sector defined benefit pensions are insured by the Pension Benefit Guaranty Corporation up to approximately $7,400/month for a retiree at age 65 in 2026. If your employer goes bankrupt and the pension is underfunded, PBGC takes over and pays your benefit up to the guarantee limit. 401(k) accounts are held separately from employer assets and are protected by ERISA. If your employer goes bankrupt, your 401(k) balance is still yours. Creditors cannot reach it.