2 answers
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In the first sentence, "below" is being used as an adjective, telling us about the bar graph.http://www.uottawa.ca/academic/arts/writcent/hypergrammar/adjectve.html
You can write it as you have in the second version, but that sentence is considered "wordy." (Too many words to say something simpler.) The first sentence is better.
http://grammar.ccc.commnet.edu/grammar/concise.htm
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