Table 2 Panel unit root tests...

Table 2

Panel unit root tests (clarified)

Variable	IPS W-stat (level)	p-value	Fisher-ADF (level)	Fisher-ADF (1st diff.)	I(?)
GDP growth	−5.94	0.000	z = −9.11	–	I(0)
Adjusted net savings	−3.21	0.001	z = −4.88	–	I(0)
Total debt service (% exports)	1.24	0.893	z = 0.52	z = −7.84	I(1)
Total debt service (% GNI)	0.87	0.808	z = 0.74	z = −6.91	I(1)
External debt stocks (% GNI)	1.56	0.941	z = 1.03	z = −5.64	I(1)
Natural resource rents	−1.02	0.154	z = −1.44	z = −8.21	I(1)
Terms of trade index	−0.44	0.330	z = −0.88	z = −6.72	I(1)
Governance index (PCA)	−0.71	0.239	z = −0.63	z = −5.29	I(1)
Current account (% GDP)	−0.89	0.187	z = −1.12	z = −7.42	I(1)

Variable	IPS W-stat (level)	p-value	Fisher-ADF (level)	Fisher-ADF (1st diff.)	I(?)
GDP growth	−5.94	0.000	z = −9.11	–	I(0)
Adjusted net savings	−3.21	0.001	z = −4.88	–	I(0)
Total debt service (% exports)	1.24	0.893	z = 0.52	z = −7.84	I(1)
Total debt service (% GNI)	0.87	0.808	z = 0.74	z = −6.91	I(1)
External debt stocks (% GNI)	1.56	0.941	z = 1.03	z = −5.64	I(1)
Natural resource rents	−1.02	0.154	z = −1.44	z = −8.21	I(1)
Terms of trade index	−0.44	0.330	z = −0.88	z = −6.72	I(1)
Governance index (PCA)	−0.71	0.239	z = −0.63	z = −5.29	I(1)
Current account (% GDP)	−0.89	0.187	z = −1.12	z = −7.42	I(1)

Note(s): IPS = Im–Pesaran–Shin test; Fisher-ADF = Maddala–Wu test. ***p < 0.01. I(0): stationary in levels. I(1): stationary after first differencing. Clarification on unit root classification (Reviewer 2, Comment 10): The Fisher-ADF test reports inverse chi-squared statistics (z-scores); values further from zero indicate stronger rejection of the unit root null. For tot_debt_exp, the level z-statistic of 0.52 fails to reject the unit root at conventional levels (p = 0.70), confirming I(1) classification. The first-difference z-statistic of −7.84 strongly rejects the unit root (p < 0.001). The current account balance (cur_acc_gdp) results are now reported: level z = −1.12 (p = 0.13), first-difference z = −7.42 (p < 0.001), confirming I(1)

Source(s): Author's computation using Stata 18 (2025)

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