. xtreg wio_sum change_m_city_r wlev wmv wroe wage wbeta wfirst soe wrmrf wmturn wmvol term1-term16, fe vce(robust)
note: wage omitted because of collinearity
note: term13 omitted because of collinearity
note: term14 omitted because of collinearity
note: term15 omitted because of collinearity
note: term16 omitted because of collinearity
上市公司年龄（已上市月份数wage）在回归中显示 wage omitted because of collinearity，这是为什么呢，该怎么解决