Designing Charts: Using Zero Baselines

A zero baseline is the point where the axis of a chart starts at zero, making it easy to compare values and assess differences more accurately. It is essential to use a zero baseline in charts, like bar and column charts, where the length or height of the bars represents a value directly. 


Determining when to use a zero baseline
  • Display data accurately: If the goal of your visualization is to give an honest and precise representation of your data, a zero baseline is crucial. For example, when showing sales figures, using a zero baseline helps the audience quickly understand the sales difference between two time periods.  
  • Easy comparisons: Using a zero baseline can simplify comparisons if you are comparing different data items. For instance, when comparing the population of multiple countries on a bar chart, a zero baseline will easily show which country has the highest or lowest population.


When to NOT use a zero baseline
  • Focus on small differences or trends: A zero baseline might not be helpful when visualizing data focusing on understanding small differences or trends. In that case, a line or area chart can be used instead. For instance, if you want to show the fluctuation of stock prices within a short period, a line chart without a zero baseline will help focus more on the trend.
  • Logarithmic scale: When visualizing data that span multiple orders of magnitude, a logarithmic scale could be more appropriate, and a zero baseline may not be used. For example, a chart showing earthquake magnitudes or the growth of social media users over the years would benefit from a logarithmic scale.

In conclusion, determining when to use a zero baseline depends on the type of data you are visualizing and the goals of your chart. Generally, a zero baseline is beneficial when displaying data that requires accurate and easy comparisons. Still, other visualization methods might be more suitable when focusing on minor differences or trends within the data.