I'm not sure where I first saw this chart, and hopefully it wasn't in class. This visualization was released by The Federal Reserve Bank of Minneapolis.
The visualization is an interactive one and lets the user view different recession trends from any of the 11 years of separate recessions. By selecting a year, it is added to the chart, along with a black diamond to represent the point of recovery.
In this view, the chart does a good job displaying and comparing a few trends, especially with the addition of a point of recovery.
In the screenshot to the left, it is easy to infer that the current recession has changed far more than the 1981 and 2001 recessions. In addition, we can also infer that the point of recovery took longer to come about, suggesting that the current recession will take longer to recover from in the long run. The only thing noticeable in this view is the colors used for each year. Instead of having an entirely separate legend for the years, it may be easier to combine the year selection and the legend into one. This way, once users select a year, they automatically know what color it will be in on the chart. This removes the need for the user to do two steps instead of one. In addition, this tactic also saves space. Another note is the colors used to depict each year. Some of the colors used are very difficult to tell apart (Ex: two shades of orange used for 1948 and 1973). The color used for 1960 appears to be the same as the background of the chart, making it hard to read when selected. The color used for 1969 is hard to see on the background as a whole. The colors themselves are difficult to remember and keep track of. Since the chart is interactive, it may benefit the user if they could simply rollover a line on the chart, and the chart tell them which year their looking at. This way, users are only concerned with colors for the years that they are currently looking at.
The aesthetics and easy use of the chart really begin to breakdown when the user decides to view all of the years at once. To the left is a screenshot of this exact situation. As anyone can see, the lines are extremely cluttered and the different shades of colors, really become apparent and difficult to differentiate. For this kind of view, a more generalized version would be easier to compare all of the different years. This view also amplifies all of the problems discussed earlier. Colors that are alike become especially difficult to differentiate, such as the orange hues of 1948 and 1973. In the chart they cross paths and it becomes difficult to follow the lines for each year.
The visualization tries to simply some of the views by adding a separate view, just for viewing the recoveries. Recoveries are shown as the time after a point of recovery. Again, this view is ideal for comparing a few years against one another, but fails when comparing all years together.