Bar graphs are good for showing how data change over time.
Example:
Advantages
show each data category in a frequency distribution
display relative numbers or proportions of multiple categories
summarize a large data set in visual form
clarify trends better than do tables
estimate key values at a glance
permit a visual check of the accuracy and reasonableness of calculations
be easily understood due to widespread use in business and the media
Disadvantages
require additional explanation
be easily manipulated to yield false impressions
fail to reveal key assumptions, causes, effects, or patterns
