急求各位小伙伴帮我看看，命令什么地方做错了，一真显示year> invalid name

gen rss=.
forvalues year=2001/2013{
gen d=(year>`i')
gen gangaid=gangai*d
qui reg ly1 gangai gangaid
qui replace rss=e(rss) in `i'
drop d gangaid
}