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Table 1: Baseline patient data for 2001–2007
Clipping Coiling P
No. 5219 5405 
Mean age (SD) 53.3 (11.6) 56.1 (13.2) <.0001
Race (No.) (%) 
    White 2695 (76.2) 2840 (78.3) .06
    Black 361 (10.2) 359 (9.9) 
    Hispanic 335 (9.5) 283 (7.8) 
    Asian 55 (1.6) 70 (1.9) 
    Native American 18 (0.5) 16 (0.4) 
    Other 75 (0.2) 61 (1.7) 
Female (No.) (%) 3878 (74.6) 4064 (75.5) .27
Hospital volume stratification (No.) (%) 
    ≤5 Cases per year 1237 (23.7) 499 (9.2) <.00001
    6–20 Cases per year 1996 (38.2) 1632 (30.2) 
    21–44 Cases per year 944 (18.1) 1453 (26.9) 
    ≥45 Cases per year 1042 (20.0) 1821 (33.7) 
Physician volume stratification (No.) (%) 
    ≤5 Cases per year 1494 (49.2) 1241 (35.8) <.0001
    6–10 Cases per year 432 (14.2) 488 (14.1) 
    11–20 Cases per year 439 (14.5) 611 (17.6) 
    ≥21 Cases per year 670 (22.1) 1124 (32.5)

	Clipping	Coiling	P
No.	5219	5405
Mean age (SD)	53.3 (11.6)	56.1 (13.2)	<.0001
Race (No.) (%)
White	2695 (76.2)	2840 (78.3)	.06
Black	361 (10.2)	359 (9.9)
Hispanic	335 (9.5)	283 (7.8)
Asian	55 (1.6)	70 (1.9)
Native American	18 (0.5)	16 (0.4)
Other	75 (0.2)	61 (1.7)
Female (No.) (%)	3878 (74.6)	4064 (75.5)	.27
Hospital volume stratification (No.) (%)
≤5 Cases per year	1237 (23.7)	499 (9.2)	<.00001
6–20 Cases per year	1996 (38.2)	1632 (30.2)
21–44 Cases per year	944 (18.1)	1453 (26.9)
≥45 Cases per year	1042 (20.0)	1821 (33.7)
Physician volume stratification (No.) (%)
≤5 Cases per year	1494 (49.2)	1241 (35.8)	<.0001
6–10 Cases per year	432 (14.2)	488 (14.1)
11–20 Cases per year	439 (14.5)	611 (17.6)
≥21 Cases per year	670 (22.1)	1124 (32.5)