Table 1.

Trends in Hospital Volumes of Medicare Patients and the Proportion of Medicare Patients Who Underwent Cancer and Cardiovascular Operations in High-Volume Hospitals, from 1999 through 2008.^*

Variable	Period
	1999–2000	2001–2002	2003–2004	2005–2006	2007–2008
Esophagectomy
No. of hospitals	1734	1632	1524	1403	1309
No. of patients	8805	8864	8694	8674	8719
Hospital volume
Median	4	5	5	7	7
Interquartile range	2–10	2–11	2–14	3–16	3–17
Market concentration (%)	39	40	43	45	44
Pancreatectomy
No. of hospitals	1308	1303	1110	1016	978
No. of patients	6633	7486	8215	8932	10,350
Hospital volume
Median	5	6	10	13	16
Interquartile range	2–14	2–17	3–22	4–28	5–35
Market concentration (%)	42	46	49	51	52
Lung resection
No. of hospitals	2408	2285	2200	2096	2045
No. of patients	49,056	49,723	51,362	53,456	56,307
Hospital volume
Median	18	19	21	23	25
Interquartile range	9–32	10–35	10–37	11–42	12–49
Market concentration (%)	39	40	39	41	41
Cystectomy
No. of hospitals	1817	1723	1607	1505	1366
No. of patients	11,258	11,593	11,953	12,278	13,167
Hospital volume
Median	5	6	6	8	10
Interquartile range	2–10	3–13	3–16	3–22	4–27
Market concentration (%)	35	40	43	47	47
AAA repair
No. of hospitals	2339	2159	2035	1949	1860
No. of patients	56,333	66,909	64,645	67,288	71,170
Hospital volume
Median	22	32	31	33	32
Interquartile range	11–42	15–62	16–56	17–58	17–57
Market concentration (%)	40	44	42	40	37
CABG
No. of hospitals	1073	1095	1142	1172	1195
No. of patients	393,043	376,016	337,430	284,252	256,716
Hospital volume
Median	244	214	179	148	130
Interquartile range	139–408	129–366	110–304	90–249	80–216
Market concentration (%)	32	31	31	31	30
Carotid endarterectomy
No. of hospitals	2635	2550	2502	2415	2341
No. of patients	232,388	232,103	222,168	190,906	178,070
Hospital volume
Median	77	78	75	67	64
Interquartile range	40–131	40–130	40–125	36–109	35–105
Market concentration (%)	39	38	37	37	35
Aortic-valve replacement
No. of hospitals	1013	1064	1105	1139	1161
No. of patients	74,541	80,223	85,556	87,421	95,033
Hospital volume
Median	53	54	57	53	60
Interquartile range	28–99	29–105	30–104	29–102	31–108
Market concentration (%)	37	37	37	37	38

^*Hospital volume is the number of Medicare patients per year. Market concentration is defined as the proportion of Medicare patients undergoing surgery in the top decile of hospitals by volume per 2-year period. AAA denotes abdominal aortic aneurysm, and CABG coronary-artery bypass grafting.