The three pie charts show changes in the expenditure of a school on various aspects in three particular years.
It is clear that, teachers' salaries was the aspect which required the highest amount, though the least money was allocated to insurance. On the other hand, expenses in other workers' payments went down considerably, while there were variations in the percentage of other categories
Although the proportion of total spending on teachers' salaries went up to 50 percent in 1991 from 40 percent in 1981, then the figure fell to 45% at the end of the period.
On the other hand, the same index for other workers' pays declined significantly with figure falling from 25% in 1981 to 15% in 2001.
Although there were some changes in the costs of the other aspects, the proportion of insurance, which equaled to only 2% in the beginning, grew four times still staying the lowest in 2001. 
The three pie charts  
show
  changes
 in the expenditure of a school on various aspects in three particular years.
It is  
clear
 that, teachers' salaries was the aspect which required the highest amount, though the least money  
was allocated
 to insurance. On the  
other
 hand, expenses in  
other
 workers' payments went down  
considerably
, while there were variations in the percentage of  
other
  categories
Although the proportion of total spending on teachers' salaries went up to 50 percent in 1991 from 40 percent in 1981, then the figure fell to 45% at the  
end
 of the period.
On the  
other
 hand, the same index for  
other
 workers' pays declined  
significantly
 with figure falling from 25% in 1981 to 15% in 2001.
Although there were  
some
  changes
 in the costs of the  
other
 aspects, the proportion of insurance, which equaled to  
only
 2% in the beginning, grew four times  
still
 staying the lowest in 2001.