This page lists DVOA (Defense-adjusted Value Over Average) for total defense as well as rushing and passing defense separated. The DVOA system is explained here. DVOA stats are adjusted to an average percentage of fumbles recovered by the offense. Quarterback scrambles are counted as passing plays rather than rushing plays. Defenses are adjusted for playing indoors.
Remember, since positive numbers represent more scoring, defense is better when it is NEGATIVE.
Regular season only.
Note for 1987: strikebreaker games (Weeks 4-6) are not included.