Table 4 Maximum likelihood estimates of group-specific stochastic production frontier model

Production frontier

 Constant

\({\beta }_{0}\)

5.535**

0.091

5.462*

0.126

5.637**

0.118

5.610**

0.094

 \(\mathrm{ln land}\)

\({\beta }_{1}\)

0.106**

0.018

0.105***

0.006

0.113**

0.011

0.105***

0.007

 \(\mathrm{ln labor}\)

\({\beta }_{2}\)

0.142***

0.024

0.171**

0.017

0.168**

0.019

0.156**

0.020

 \(\mathrm{ln fertilizer}\)

\({\beta }_{3}\)

0.201*

0.106

0.209***

0.032

0.237***

0.021

0.206***

0.014

 \(\mathrm{ln seed}\)

\({\beta }_{4}\)

0.128**

0.035

0.138***

0.021

0.166*

0.047

0.135***

0.017

Socio-economic variables

 Constant

\({\delta }_{0}\)

− 2.379

0.152

− 2.794***

0.054

− 2.984**

0.083

− 2.781***

0.061

 Age

\({\delta }_{1}\)

0.003*

0.010

0.007

0.009

− 0.031

0.015

0.002

0.006

 Gender

\({\delta }_{2}\)

− 0.795**

0.249

− 0.728***

0.233

− 0.647***

0.220

− 0.737***

0.224

 Education

\({\delta }_{3}\)

− 0.151***

0.048

− 0.334**

0.084

− 0.428*

0.131

− 0.237***

0.060

 Household size

\({\delta }_{4}\)

− 0.068

0.065

− 0.032

0.052

0.074

0.214

− 0.035

0.057

 Coop. membership

\({\delta }_{5}\)

− 0.144

0.311

− 0.152

0.339

− 0.313*

0.384

− 0.153

0.376

 Extension services

\({\delta }_{6}\)

− 0.135*

0.022

− 0.021***

0.011

− 0.019**

0.009

− 0.027**

0.013

 Credit access

\({\delta }_{7}\)

0.192

0.047

− 0.354**

0.097

− 0.213***

0.030

− 0.272***

0.029

 Off− farm income

\({\delta }_{8}\)

− 0.144

0.141

− 0.275

0.406

0.310

0.513

− 0.112

0.112

 Land tenure

\({\delta }_{9}\)

− 0.326***

0.317

− 0.352**

0.109

− 0.285***

0.116

− 0.302**

0.129

 Livestock ownership

\({\delta }_{10}\)

− 0.801**

0.123

− 0.723***

0.065

− 0.476**

0.155

− 0.716***

0.086

Model diagnostics

 Sigma− u

\({\sigma }_{u}\)

0.127***

0.011

0.132***

0.009

0.122***

0.020

0.111***

0.013

 Sigma− v

\({\sigma }_{v}\)

0.094***

0.013

0.079***

0.008

0.105**

0.009

0.064***

0.006

 Variance

\({\sigma }^{2}\)

0.025***

0.002

0.024***

0.003

0.026**

0.001

0.016***

0.002

 Lambda

\(\lambda \)

1.351***

0.075

1.671***

0.104

1.162***

0.022

1.718***

0.018

 Log likelihood function

\(LLF\)

− 416.351

− 313.237

− 504.115

− 348.808

 No. of observations

91

202

67

360