Table 5 Parameter estimates for conventional and selectivity SPF models: Matched sample

lnENGINEOPER

0.79***

(0.07)

0.66***

(0.13)

0.84***

(0.09)

0.70***

(0.17)

0.83***

(0.11)

lnFUELCOST

0.10**

(0.04)

0.16***

(0.06)

0.08

(0.05)

0.14*

(0.08)

0.08

(0.06)

lnLEADERSEMP

0.18**

(0.08)

0.08

(0.12)

0.23**

(0.11)

0.09

(0.18)

0.23*

(0.12)

lnHELPERSEMP

 − 0.07

(0.14)

0.22

(0.20)

 − 0.20

(0.18)

0.20

(0.30)

 − 0.21

(0.20)

lnUSEFULSEINE

0.06**

(0.04)

0.09**

(0.04)

0.05

(0.03)

0.10

(0.05)

0.05

(0.04)

ONDO

0.09**

(0.04)

0.12

(0.10)

0.07

(0.05)

0.05

(0.13)

0.05

(0.06)

AKWA-IBOM

0.08*

(0.04)

0.16**

(0.08)

0.05

(0.05)

0.11

(0.10)

0.04

(0.06)

SHOCK

0.07**

(0.03)

0.07

(0.06)

0.08**

(0.04)

0.06

(0.08)

0.09*

(0.05)

HIGHENGCAP

 − 0.12

(0.10)

 − 0.30**

(0.14)

 − 0.02

(0.13)

 − 0.30

(0.22)

 − 0.01

(0.19)

FISHVILL

 − 0.02

(0.03)

 − 0.10*

(0.05)

0.01

(0.04)

 − 0.12

(0.09)

0.01

(0.05)

Leadercontrol

 − 0.04

(0.05)

0.02

(0.07)

 − 0.07

(0.06)

 − 0.02

(0.09)

 − 0.07

(0.06)

Helpercontrol

 − 0.04

(0.10)

0.16

(0.16)

 − 0.12

(0.13)

0.14

(0.26)

 − 0.13

(0.15)

MEMBERSHIP

0.12***

(0.04)

Constant

9.29***

(0.48)

8.49***

(0.70)

9.73***

(0.63)

8.70***

(0.94)

9.66***

(0.72)

λ

1.19***

(0.06)

1.20***

(0.19)

1.28***

(0.07)

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

0.13***

(0.02)

0.09***

(0.04)

0.14***

(0.02)

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

0.24*

(0.12)

0.28***

(0.07)

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

0.20***

(0.05)

0.25***

(0.04)

\({\rho }_{(w,v)}\)

0.45

(0.52)

 − 0.33

(0.34)

Return to scale

1.13

0.91

1.07

0.84

1.06

Number of obs

350

92

258

92

258

Log likelihood

 − 52.17

0.67

 − 46.22

 − 80.01

 − 113.68