Table 3. Decomposition of concentration indices (C) and changes in concentration index in utilization of cataract surgery, Shahroud, Iran .

Variables	First phase of study in 2009		Second phase of study in 2014		Changes in Concentration Index
	Contribution to overall C	Contribution percent	Contribution to overall C	Contribution Percent	Contribution to change in C	Contribution Percent
Need variables
Gender (Female)	0.001	1.7	0.010	4.5	0.009	11.2
Age (Year)	0.008	10.5	0.070	30.1	0.054	67.5
Diabetes (Yes)	0.000	0.2	0.011	4.7	0.011	13.7
Having cataract (Yes) (Grade>= 2)	0.002	3.4	0.005	2.3	0.005	6.3
Hypertension (Yes)	0.001	1.4	0.002	1.0	0.001	1.2
Smoking (Yes)	-0.000	0.5	-0.004	-1.7	-0.004	-5.0
Need Total	0.012	17.7	0.094	40.9	0.082
Non-need variables
Complementary Insurance (Yes)	0.005	12.6	0.006	6.5	0.001	1.2
Education (Year)	0.022	32.6	0.036	39.1	0.014	17.5
Economic Quintiles
Quintile 1 (Low)	Reference		Reference		Reference
Quintile 2	-0.001	-14.0	-0.016	-7.1	-0.017	-21.2
Quintile 3	0.010	12.4	0.002	0.29	-0.008	-10.0
Quintile 4	0.018	20.7	0.041	17.7	0.023	28.7
Quintile 5 (High)	0.044	50.0	0.090	38.6	0.046	57.5
Non-Need Total	0.060	114.3	0.126	95.0	0.066
Horizontal Inequity Index	0.080		0.166