How many percentage points did the purchasing power of social transfers increase by from 1981 to 1982?
return social transfers ;return the  purchasing power of #1 ;return #2 in  1981 ;return #2 in  1982 ;return percentage of #3 ;return percentage of #4 ;return difference of #6 and  #5
['select', 'project', 'filter', 'filter', 'project', 'project', 'arithmetic']