Data Visualization with Period-Over-Period Charts

One of the most common chart types you will see—and likely use—is a period-over-period chart. This chart will allow you to see trends and changes when comparing data from two similar periods.

For example, you may typically have very strong retail sales in the fourth quarter. Since these sales are typically a lot higher than the first three quarters it is useful to compare Q4 sales this year to the Q4 sales from the previous year. This gives a better indication of current performance based on the most comparable previous period.

As one of the more simple data visualization tools, a period-over-period chart requires only two fields: the x-axis column that includes the period data, and the y-axis column which shows value data. This chart is versatile, allowing you to visualize the data in a number of different ways, most often using bars or line graphs.

This chart is an important data visualization you can use to track your key performance indicators (KPIs) over time. Because understanding growth or decline is essential to business success, a period-over-period chart will be something you can utilize across a wide range of business cases.

When to Use a Period-Over-Period Chart

You should use a period-over-period chart when you want to compare data from different periods (like multiple years), emphasizing changes in the data. It shows the relationship between large quantities of data, bringing out important trends.

Tracking annual sales becomes more impactful when you compare the current period to the most comparable previous period. Now you can discover growth patterns to better understand if your sales are going up this quarter versus the same quarter last year.

While handy for capturing trends, this chart can also be helpful in comparing metrics. Use tools like a grouped bar chart and a trendline together to compare similar metrics. For example, with a grouped bar chart you can track how each sales team member performed for the quarter. The trendline will show how the group as a whole performed, allowing you to compare each team member’s performance.

Business Use Cases for Period-Over-Period Charts

Period-over-period charts always involve performance over time but can be used to discover many business insights like the following:

• Digital Promotions.Use a period-over-period chart to track web traffic over time. Once you understand seasonal shifts in web traffic, you can plan promotions and content for digital distribution.
• Market Research.Use a period-over-period chart to track trends in key issues. You could track responses on the most important issues facing your target customers and see which issues trend higher or lower over time. Customize messaging based on those trends.
• Performance metrics.Track how teams are performing against previous years or current goals. Data visualizations make it easy to track merit-based bonuses tied to growth KPIs. Additionally, you can track if team members need additional support during historically busy months.
• Budget spend.Use a period-over-period chart to track qualified leads from different industry events over the past several years. Add a trend line to show the number of financial resources dedicated to those events. This will allow you to see what type of events are most effective and budget resources for future events.
• Forecasting.After using a period-over-period chart to track sales across many years, you could begin to forecast future sales.
• Year over year.You can use a period-over-period chart to highlight statistical values like the percent change in Q1 last year vs Q1 of this year. Seeing the percentage of growth or decline can tell a clearer story than just charting values.

Regardless of which department utilizes it, a period-over-period chart is your best tool when you want to highlight variations in data over time.

Utilizing Period-Over-Period Chart Components

Using trend lines and bars in a period-over-period chart is one of the simplest ways to visualize data. Seeing the movement of a line or bars up or down helps to bring the story behind the data to the forefront.

However, there are a number of ways you can use a period-over-period chart in a business intelligence dashboard. Moving beyond bars and lines, it’s any way you choose to show changes over periods.

Some examples of different ways to visualize this data include:

• Comparison — compare one period to another with bars or lines showing changes over time.
• Variance — highlight the difference with the periods shown as bars and variance values shown as lines.
• Trend — use lines or grouped bar charts to visualize multiple periods. This type of chart allows you to better compare the subgroups within your time period and how they perform against a primary trend.
• Gauge — show only the value of the change with a number or a visual icon (like a green up arrow or red down arrow) indicating the difference.
• Table — display data in a table with a row for each group and include a sparkline or column highlighting the percent of change.
• Progress bar — use this to see a comparison between two time periods. It can be most useful if you’re comparing time periods that are unequal, like last quarter’s performance numbers to this quarter’s to-date performance.

Additionally, you can combine these visualization tools in your dashboard in any number of ways.

Tips for Using Period-Over-Period Charts

There are some key points to consider when utilizing a period-over-period chart to visualize your metrics.

Use comparable measurement intervals.

Use a similar data range to compare. Don’t use a full year’s data compared to a single quarter – use comparable periods. Additionally, use the right interval size for the business questions you are working to answer. If your data intervals are too large, it could mean it takes too long to see where the data is trending. But if they are too short, it can create a lot of noise on your chart and bury the story.

Be wise with data visualization.

Use visual cues effectively. Use solid lines and colors with muted, contrasting colors to show different values. Adopt stronger colors and lines to highlight variances or key points of data.

While you can track a number of key data points, limit your comparisons to only four or five trendlines of data. While most tools are capable of highlighting many more data points, it will create a busy chart with too many visual distractions to understand the meaning.

Understand your baseline value.

Be conscious that your baseline value – whether you start at zero or 10 million can change the accuracy of the way your data is presented. For bar charts, starting with zero helps to give the data better meaning and allow true comparisons. This way you don’t misrepresent comparisons because the ratios of lengths and values will match up. Line charts, however, function differently and you may want to start your baseline at a number that best highlights the changes in value.

The period-over-period chart is one of the most essential data visualization tools for tracking key business metrics. To learn more about other charts and data visualization techniques, see our articles below.