求翻译：下表显示了从1991年到2011年该校大学生所购买的书籍类别的变化，科学类别的书籍比例逐年下降，而计算机类别的书却在逐年增加。是什么意思？

The following table shows the changes in the types of books purchased from 1991 to 2011 school students, the proportion of scientific categories of books is declining, and computer classes book has increased year by year.

The following table shows from 1991 to 2011 the School of the university students have purchased books category of the change, the scientific category of the books share has been declining, and the computer of the book category has been increasing year by year.

Next extolled has shown from 1991 the books category change which this school university student purchased to 2011, the scientific category books proportion dropped year by year, but the computer category book year by year was increasing actually.

Following table shows from 1991 to 2011 the changes of college students buying books category, Scientific categories declining proportion of books, and books of computer category are on the increase year by year.

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