Computing Quarterly and Yearly Averages

Quarterly averages were computed by averaging Republican, Democrat, and Independent figures for individual polls within each quarter. Yearly averages were then calculated using the quarterly averages within each year. Additional averages were calculated for specific time segments as follows: Pre-9/11 Baseline (January to August 2001), Early Post-9/11 (October 2001 to June 2002), Later Post-9/11 (July to December 2002), Run-Up to Iraq War & Major Combat (January to May 2003), Post-Major Combat (July to December 2003), Democratic Primaries/Pre-Democratic Convention (January to July 2004), Post-Democratic Convention (July to August 2004), Post-GOP Convention (early September 2004), Post-First Debate (late September to early October 2004), and Late Campaign (October 2004).