How can a bar graph be used to show trends?

Arrange your bar graph so that each bar is a separate time period (weeks, months, financial years, etc.) along the x-axis and the values for those time periods are represented on the y-axis. For example, you could have a bar graph where each bar represents the number of widget sales per year and each bar is a separate year (e.g. 2000, 2001, 2002). This could be used to show a trend in annual widget sales over several years.