. xtunitroot ips trade ,demean
Im-Pesaran-Shin unit-root test for trade
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Ho: All panels contain unit roots Number of panels = 107
Ha: Some panels are stationary Avg. number of periods = 39.76
AR parameter: Panel-specific Asymptotics: T,N -> Infinity
Panel means: Included sequentially
Time trend: Not included Cross-sectional means removed
ADF regressions: No lags included
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Fixed-N exact critical values
Statistic p-value 1% 5% 10%
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t-bar -1.5105 (Not available)
t-tilde-bar -1.4381
Z-t-tilde-bar 0.2215 *
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* Normality of Z-t-tilde-bar requires at least 10 observations
per panel with unbalanced data.
为什么会出现上面的情况呢??