From ~4 points (1950s) to ~2.3 points (2020s) 2. **Six components** - Crowd, travel, familiarity, referee, climate, routine 3. **Team variation** - Seattle/KC at ~3.5 points, others at ~2 points 4. **Travel effects** - West-to-east worse than east-to-west 5. **Playoff boost** - HFA increases 1-2 poi