Question: When +18.1 is the ± yes side 2008 percentage what is the percentage of against?
Schema: create table table_20683381_3 (against___percentage_ varchar, ±_yes_side_2008___percentage_ varchar, PRIMARY KEY (against___percentage_))
SQL: select against___percentage_ from table_20683381_3 where ±_yes_side_2008___percentage_ = "+18.1"