Table 1 Descriptive statistics of outcome variable, main interest, patient characteristics and hospital characteristics

Outcome variable

 Deaths, n (%)

2,421 (0.9)

1,543 (1.1)

2,791 (2.5)

1,924 (5.8)

790 (7.7)

 30-day unplanned readmissions, n (%) ^a

28,120 (18.4)

15,425 (16.2)

8,319 (12.7)

3,892 (20.6)

808 (13.9)

Main Interest

 \(\ln(HHI_i^{pat})\), mean ± SD

-2.12 ± 0.58

-2.00 ± 0.52

-1.98 ± 0.67

-1.49 ± 0.42

-1.23 ± 0.43

Patient characteristics

 Age, mean ± SD

73.06 ± 9.72

70.69 ± 11.15

61.88 ± 17.54

65.61 ± 12.8

68.95 ± 12.49

Gender

 Female, n (%)

92,699 (35.8)

67,218 (45.9)

57,693 (51.3)

12,900 (39.2)

3,411 (33.1)

 Male, n (%)

166,536 (64.2)

79,384 (54.1)

54,709 (48.7)

19,997 (60.8)

6,882 (66.9)

Health Insurance program

 UEBMI, n (%)

70,786 (27.3)

39,901 (27.2)

42,403 (37.7)

5,301 (16.1)

2,811 (27.3)

 URBMI, n (%)

106,675 (41.1)

63,557 (43.4)

38,331 (34.1)

13,778 (41.9)

4,356 (42.3)

 NCMS, n (%)

52,691 (20.3)

25,558 (17.4)

17,965 (16.0)

7,889 (24.0)

1,370 (13.3)

 Self-pay, n (%)

8,400 (3.2)

7,095 (4.8)

6,694 (6.0)

3,162 (9.6)

992 (9.6)

 Other, n (%)

20,683 (8.0)

10,491 (7.2)

7,009 (6.2)

2,767 (8.4)

764 (7.4)

Surgical procedures

 No, n (%)

238,903 (92.2)

132,496 (90.4)

95,975 (85.4)

21,104 (64.2)

3,284 (31.9)

 Yes, n (%)

20,332 (7.8)

14,106 (9.6)

16,427 (14.6)

11,793 (35.8)

7,009 (68.1)

CCI, mean ± SD

0.8 ± 1.16

1.38 ± 1.29

1.14 ± 1.48

0.71 ± 1.18

0.8 ± 1.16

Admission source

 Emergency, n (%)

47,455 (18.3)

38,282 (26.1)

24,809 (22.1)

18,510 (56.3)

5,631 (54.7)

 Outpatient, n (%)

209,268 (80.7)

106,776 (72.8)

86,578 (77.0)

13,713 (41.7)

4,441 (43.1)

 Others, n (%)

2,512 (1.0)

1,544 (1.1)

1,015 (0.9)

674 (2.0)

221 (2.1)

Hospital characteristics

 Hospital level

  Primary, n (%)

15,948 (6.2)

5,510 (3.8)

3,960 (3.5)

52 (0.2)

-

  Secondary, n (%)

96,214 (37.1)

53,574 (36.5)

38,577 (34.3)

9,004 (27.4)

666 (6.5)

  Tertiary, n (%)

103,472 (39.9)

72,023 (49.1)

55,770 (49.6)

23,257 (70.7)

9,542 (92.7)

  Un-graded, n (%)

43,601 (16.8)

15,495 (10.6)

14,095 (12.5)

584 (1.8)

85 (0.8)

Whether public hospital

 No, n (%)

80,192 (30.9)

35,094 (23.9)

26,658 (23.7)

2,188 (6.7)

171 (1.7)

 Yes, n (%)

179,043 (69.1)

111,508 (76.1)

85,744 (76.3)

30,709 (93.3)

10,122 (98.3)

Whether for-profit hospital

 No, n (%)

206,364 (79.6)

124,329 (84.8)

96,640 (86.0)

31,667 (96.3)

10,230 (99.4)

 Yes, n (%)

52,871 (20.4)

22,273 (15.2)

15,762 (14.0)

1,230 (3.7)

63 (0.6)

Whether general hospital

 No, n (%)

51,439 (19.8)

36,327 (24.8)

19,526 (17.4)

5,187 (15.8)

685 (6.7)

 Yes, n (%)

207,796 (80.2)

110,275 (75.2)

92,876 (82.6)

27,710 (84.2)

9,608 (93.3)

Month

 October, n (%)

76,593 (29.5)

49,252 (33.6)

32,485 (28.9)

9,750 (29.6)

3,054 (29.7)

 November, n (%)

78,022 (30.1)

47,548 (32.4)

34,510 (30.7)

10,476 (31.8)

3,382 (32.8)

 December, n (%)

104,620 (40.4)

49,802 (34.0)

45,407 (40.4)

12,671 (38.5)

3,857 (37.5)

Year

 2017, n (%)

118,633 (45.8)

60,309 (41.1)

46,309 (41.2)

15,438 (46.9)

4,172 (40.5)

 2019, n (%)

140,602 (54.2)

86,293 (58.9)

66,093 (58.8)

17,459 (53.1)

6,121 (59.5)