Table 3.

Decomposition of the concentration index for stunting (1996 & 2016)

Variables	Marginal effect				Weighted mean (1996: Meanstunted = 0.553; 2016: Meanstunted = 0.337)		Concentration Index (C) (1996: Cstunted = − 0.082;2016: Cstunted = − 0.138)		Absolute contribution		Percentage contribution (%)		Change
	1996	P value	2016	P value	1996	2016	1996	2016	1996	2016	1996	2016
Mother’s education
Primary	−0.030	0.331	− 0.048	0.173	0.113	0.186	0.157	−0.179	− 0.0010	0.0048	1.2	−3.7	−4.9
Secondary and above	−0.085*	0.020	−0.023	0.558	0.099	0.480	0.575	0.191	−0.0087	−0.0062	11.0	4.7	−6.3
Sub-total									−0.0097	− 0.0014	12.2	1.1	− 11.1
Husband/Partner’s education
Primary	−0.035	0.143	0.015	0.725	0.244	0.231	−0.070	−0.257	0.0011	−0.0027	−1.4	2.1	3.5
Secondary and above	−0.035	0.172	0.039	0.418	0.389	0.624	0.243	0.153	−0.0059	0.0110	7.4	0.8	−6.6
Sub-total									−0.0048	0.0083	6.1	2.9	−3.2
Maternal short stature (< 145 cm)	0.137*	< 0.001	0.253*	< 0.001	0.150	0.114	−0.007	− 0.089	− 0.0002	− 0.0077	0.3	5.9	5.6
Mother’s BMI
Normal (18.5 to < 25)	−0.018	0.446	−0.069*	0.042	0.711	0.634	−0.006	−0.046	0.0001	0.0060	−0.2	−4.6	−4.4
Overweight/Obese (≥25)	−0.065	0.344	−0.148*	0.003	0.018	0.176	0.350	0.285	−0.0007	−0.0221	0.9	16.9	16.0
Sub-total									−0.0006	−0.0161	0.7	12.3	11.6
Antenatal care visits	−0.002	0.930	−0.040	0.532	0.438	0.943	0.172	0.023	−0.0002	−0.0025	0.3	1.9	1.6
Delivery in health facility	−0.046	0.157	−0.007	0.806	0.082	0.573	0.573	0.179	−0.0039	−0.0021	4.8	1.6	−3.2
Children aged 25–59 months	0.172*	< 0.001	0.109*	< 0.001	0.272	0.502	0.005	0.019	0.0004	0.0031	−0.5	−2.4	−1.9
Birth order
2nd - 4th	0.076*	0.001	0.070*	0.021	0.525	0.574	0.006	−0.009	0.0005	−0.0011	− 0.6	0.8	1.4
5 or more	0.109*	< 0.001	0.130*	0.007	0.254	0.093	−0.154	− 0.281	− 0.0077	−0.0101	9.7	7.7	−2.0
Sub-total									−0.0072	−0.0112	9.1	8.6	−0.5
Breast fed children	−0.189	0.511	−0.186	0.150	0.998	0.993	−0.001	−0.0004	0.0002	0.0002	−0.2	−0.2	0.0
Perceived size of baby at birth
Average	0.052*	0.014	0.032	0.311	0.431	0.672	0.021	0.020	0.0008	0.0013	−1.1	−1.0	0.1
Small	0.156*	< 0.001	0.084*	0.039	0.259	0.164	−0.080	−0.113	−0.0058	−0.0047	7.3	3.6	−3.7
Sub-total									−0.0050	−0.0034	6.2	2.6	−3.6
Caste/Ethnicity
Janajati	−0.144*	< 0.001	−0.046	0.253	0.308	0.301	−0.013	−0.064	0.0010	0.0026	−1.3	−2.0	−0.7
Other terai caste	−0.071	0.068	−0.007	0.880	0.124	0.174	−0.020	0.165	0.0003	−0.0006	−0.4	0.5	0.9
Muslim	−0.083	0.076	−0.0002	0.998	0.058	0.059	0.068	0.185	−0.0006	0.0000	0.7	0.0	−0.7
Newar	−0.199*	< 0.001	−0.046	0.665	0.050	0.035	0.490	0.151	−0.0089	−0.0007	11.1	0.6	−10.5
Brahmin/Chhetri	−0.103*	0.002	−0.015	0.714	0.296	0.286	0.029	−0.025	−0.0016	0.0003	2.0	−0.2	−2.2
Sub-total									−0.0098	0.0016	12.1	−1.2	−13.3
Wealth quintile
Second	−0.040	0.110	−0.061	0.133	0.213	0.218	−0.291	−0.377	0.0044	0.0150	−5.6	−11.5	−5.9
Third	−0.040	0.137	−0.124*	0.002	0.194	0.215	0.116	0.057	−0.0016	−0.0045	2.0	3.5	1.5
Fourth	−0.101*	< 0.001	−0.098*	0.015	0.197	0.220	0.507	0.492	−0.0182	−0.0316	22.8	24.2	1.4
Fifth (Richest)	−0.145*	0.001	−0.200*	< 0.001	0.148	0.144	0.852	0.856	−0.0330	−0.0732	41.4	56.1	14.7
Sub-total									−0.0484	−0.0943	60.7	72.3	11.6
Open Defecation	−0.039	0.253	0.050	0.222	0.812	0.199	−0.165	−0.171	0.0095	−0.0050	−11.9	3.9	15.8
Total sum contribution									−0.0797	−0.1305
Residual (Unexplained)									−0.0021	−0.0076

Weighted N: - 1996: 2967; 2016: 1588. Average marginal effects and P values were calculated from predictions of probit model. The reference groups used were mothers with no education, husband/partner with no education, mothers who are not short, mothers who are underweight (BMI < 18.5), mothers who did not visit health facility for ANC, mothers who delivered in places others than a health facility, children aged 0–24 months, first born children, children who are not breastfed, perceived size of baby at birth large, caste/ethnicity Dalit, first wealth quintile (poorest), households with toilet facilities. The contributions of predictors to the observed socioeconomic inequality in stunting is calculated according to eq. (3) by using means, concentration indices of predictors and marginal effects. The total contribution is the sum of absolute contributions or the overall concentration index minus the residual. ^*p < 0.05