The given graph outlines the information about sales figures for lecture materials between 2002-2012.
Overall, the bar chart provides 4 different types of books, and to put it bluntly, they differ significantly. The graph indicates the changes every two years.
To begin with, the two groups of manuals exist. The first one can be conventionally named as “Leisure books”. Thus, Hobbies books were not so common at all, referring to the fact, that their point always reached lowest rates. For instance, in 2002 only 0,5 copies were printed. It underwent fluctuations by increasing and decreasing numbers every 2 years. Meanwhile Entertainment books had better positions accounting for the sum from 1 to 3 copies, which was a third of History books, which always had the highest number.
An extra point to note is a presence of a second group of books, called “ Educational manuals”. Here, it is not that hard to notice, that the highest index was reached by History books, reaching from 4,2 to 10 copies. Remarkably, they were the most frequent during the whole period. Likewise, the Art books were not so popular. Furthermore, their quantity did not always exceed previous types of books. As an example, indicators were equal with Entertainment books between 2006-2008. In other cases it outreached the Leisure books, but without significant difference, having a difference between 0,2-1 copies.