用LLC检验截面数据城市化率urban，前面没有输入“trend”选项，后面有添加“trend”，结果不加trend的检验显示不存在单位根问题，加入“trend”后反而存在单位根问题。请问1：城市化率是否具有时间趋势，个人觉得是有的吧。。
请问2：这两个完全相反的结果哪个更可信？
谢谢！


xtunitroot llc urban,lags(aic 10)demean

Levin-Lin-Chu unit-root test for urban
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Ho: Panels contain unit roots               Number of panels  =     26
Ha: Panels are stationary                   Number of periods =     27

AR parameter: Common                        Asymptotics: N/T -> 0
Panel means:  Included
Time trend:   Not included                  Cross-sectional means removed

ADF regressions: 7.19 lags average (chosen by AIC)
LR variance:     Bartlett kernel, 9.00 lags average (chosen by LLC)
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                    Statistic      p-value
------------------------------------------------------------------------------
Unadjusted t       -56.7638
Adjusted t*        -58.6482        0.0000
------------------------------------------------------------------------------

. xtunitroot llc urban,trend lags(aic 10)demean

Levin-Lin-Chu unit-root test for urban
--------------------------------------
Ho: Panels contain unit roots               Number of panels  =     26
Ha: Panels are stationary                   Number of periods =     27

AR parameter: Common                        Asymptotics: N/T -> 0
Panel means:  Included
Time trend:   Included                      Cross-sectional means removed

ADF regressions: 8.81 lags average (chosen by AIC)
LR variance:     Bartlett kernel, 9.00 lags average (chosen by LLC)
------------------------------------------------------------------------------
                    Statistic      p-value
------------------------------------------------------------------------------
Unadjusted t        -8.3061
Adjusted t*          2.3838        0.9914
------------------------------------------------------------------------------