Adding parenthesis to aea.bst style file

I am struggling to add a parenthesis to the reference list by editing the default aea.bst style file. I believe this is where the change needs to be made:

FUNCTION {output.year} % writ
{  list.year empty$
  { skip$ }
  { "(" list.year ")" * ", " * write$}
  if$
}

But I can only produce:

McAuley, Julian, and Alex Yang, 2016), “Addressing complex and subjective product-related queries with customer reviews,” 625–635, International World Wide Web Conferences Steering Committee.

with missing open parentheses