请问为什么正常生成ncskew大.doc，而生成ncskew小.doc报错invalid syntax

summ size, d
local a = r(p25)
local b=r(p75)
gen size1=cond(size<`a', 0, cond(size>`b', 1,.))//根据企业规模分组
xi:reg ncskew ovc2 ret sigma bm roa lev dturn growth fata i.year i.ind if size1==1,r
outreg2 using ncskew大.doc,replace tstat bdec(3) tdec(2) ctitle(ncskew) e(r2_a,F) addstat(F test,e(p)) addtext(ind, YES,year, YES) //生成ncskew大.doc
xi:reg ncskew ovc2 ret sigma bm roa lev dturn growth fata i.year i.ind if size1==0,r
outreg2 using ncskew小.doc,replace tstat bdec(3) tdec(2) ctitle(ncskew) e(r2_a,F) addstat(F test,e(p)) addtext(ind, YES,year, YES) //生成ncskew小.doc

软件版本stata 14.0