Fidelity Total Market Index Fund (FSKAX) is a mutual fund from Fidelity Investments (US) and State Street SPDR S&P 500 ETF Trust (SPY) is a ETF from State Street Investment Management. Over the past year FSKAX returned +21.87% while SPY returned +23.66%. Year to date, FSKAX is up 13.30% versus a gain of 13.79% for SPY.

Over three years, FSKAX compounded at +19.24% per year against +21.40% for SPY; over five years the annualized figures are +10.82% and +13.37% respectively. Across the full 5-year window we track, FSKAX has the edge at +10.82% annualized vs +8.85%. Past performance does not guarantee future results.

FSKAX has been the more volatile fund, with annualized monthly volatility of 16.2% compared with 15.3% for SPY. Lower volatility generally means a smoother ride, though it often comes with lower long-run returns.

The deepest peak-to-trough decline in our data was -26.0% for FSKAX and -56.5% for SPY. Drawdown depth is worth weighing if you expect to sell during market stress rather than ride it out.

The two funds' monthly returns correlate at 0.99. They move almost in lockstep, so holding both mostly duplicates the same exposure.

FSKAX charges 0.02% per year while SPY charges 0.09%. On a $10,000 position that is $2 vs $9 annually, a gap of $7 per year that compounds over a long holding period. On income, FSKAX currently yields 0.94% against 1.01% for SPY.