Time will tell?

Time lines are also critical when displaying data. Look at the chart below:

A clear stable increase in health care costs since 2002? Not quite. Notice how before 2004, there are 1 year steps. After, there is a gap between 2004 and 2007, and 2007 and 2009. This presentation makes us believe that healthcare expenditure increases continuously at the same rate since 2002 – but actually it doesn’t. So if you deal with time lines: make sure that the spacing between the data points are correct! Only then will you be able to see the trends correctly.