Table 1.
Sample characteristics, baseline and first waves (no. (%), mean (95% CI))
| Baseline (2000) | First wave (2003) | |||||
|---|---|---|---|---|---|---|
| Low income | High income | P value | Low income | High income | P value | |
| (29–586 USD) | (615–1851 USD) | (26–543 USD) | (543–2594 USD) | |||
| N | 694,162 | 2,150,172 | 711,684 | 2,132,650 | ||
| Place of residence | ||||||
| Urban | 410,251 (59.1%) | 1,257,923 (58.5%) | <.001 | 429,044 (60.3%) | 1,274,360 (59.8%) | <.001 |
| Suburban | 239,649 (34.5%) | 672,101 (31.3%) | 234,431 (32.9%) | 632,389 (29.7%) | ||
| Rural | 44,262 (6.4%) | 220,148 (10.2%) | 48,209 (6.8%) | 225,901 (10.6%) | ||
| Occupation categorya | ||||||
| 1 | 148,891 (21.4%) | 408,848 (19.0%) | <.001 | 150,682 (21.2%) | 385,223 (18.1%) | <.001 |
| 2 | 260,675 (37.6%) | 844,689 (39.3%) | 212,327 (29.8%) | 853,357 (40.0%) | ||
| 3 | 101 (0.0%) | 456,637 (21.2%) | 10,839 (1.5%) | 446,917 (21.0%) | ||
| 4 | 0 (0.0%) | 420,587 (19.6%) | 3201 (0.4%) | 435,063 (20.4%) | ||
| 5 | 10,542 (1.5%) | 884 (0.0%) | 14,072 (2.0%) | 643 (0.0%) | ||
| 6 | 273,953 (39.5%) | 18,527 (0.9%) | 320,563 (45.0%) | 11,447 (0.5%) | ||
| Elixhauser comorbidity index | ||||||
| 0 | 559,719 (80.6%) | 1,755,767 (81.7%) | <.001 | 547,246 (76.9%) | 1,675,097 (78.5%) | 0.015 |
| 1–3 | 129,514 (18.7%) | 383,916 (17.9%) | 160,105 (22.5%) | 450,250 (21.1%) | ||
| ≥ 4 | 4929 (0.7%) | 10,489 (0.5%) | 4333 (0.6%) | 7303 (0.3%) | ||
| Outpatient visitsb | 11.30 (11.27–11.33) | 11.52 (11.50–11.53) | <.001 | 11.41 (11.38–11.43) | 11.36 (11.35–11.38) | <.001 |
| Inpatient Staysb | 0.113 (0.112–0.114) | 0.095 (0.094–0.095) | <.001 | 0.120 (0.119–0.121) | 0.096 (0.096–0.097) | <.001 |
| Physician Density of Residenceb | 1.573 (1.569–1.577) | 1.712 (1.709–1.714) | <.001 | 1.655 (1.651–1.659) | 1.809 (1.806–1.812) | <.001 |
a Category 1 = civil servants, full-time or regularly paid personnel in governmental agencies and public schools, 2 = employees of privately owned enterprises or institutions, 3 = self-employed, other employees or paid personnel, and members of farmer and fishermen associations, 4 = military personnel, military school students, bereaved families of deceased military personnel, public service in lieu of military service, 5 = low-income citizens, 6 = veterans and dependents, and citizens without a fixed profession from other areas
b Number per 1000 patients