The three pie charts below show the changes in annual spending by a particular UK school in 1981, 1991 and 2001. Summarise the information by selecting and reporting the main features, and make comparisons where relevant.

The pie charts illustrate the expenditures of education, grouped into five categories in three years periods.

Overall

, the proportion of professors' salaries is always at the highest of all five groups, which is around 40% to 50%.

In contrast

, the lowest of costs is the insurance category, which never catches up to 10%.

According to

the figures,

this

school's spending on resources,

such

as dictionaries, accounted for 15% in 1981 and

then

rose slightly to 20% in 1991, but it decreased dramatically to 8% in 2001. There was

also

a group that had decreased, the other employees' salaries, it declined slowly from 28% to 15%. As can be seen from the second-high category in 2001, the costs of equipment, it was going up 18% compared to ten years ago, which was the second-low one in 1991. The percentages of

this

group were 15%, 5%, and 23% in 1981, 1991, and 2001 respectively.