Choosing the right chart for a recurring report

A chart in a one-off presentation only has to work once. A chart in a recurring report has to work every week, with numbers nobody has seen yet. The bar that looked balanced in January may tower over the others in June. The pie with four neat slices may have nine by the end of the year. A label that fitted last month may overlap this month.

Choosing charts for a report that refreshes is mostly about choosing charts that degrade gracefully. This piece goes through the common jobs a chart does in a recurring report, and which shapes hold up.

Start with the question the reader asks

Every chart in a recurring report should answer a question someone asks every edition. Write it down before you choose the chart:

• “Are we growing?”
• “Are we on target this month?”
• “Which region is behind?”
• “Is the backlog getting bigger or smaller?”

The question tells you the chart. If you can’t name the question, the chart probably doesn’t need to be there. If you want to see the full range of options before narrowing down, an overview of types of graphs is a handy reference.

Trends over time: lines and columns

For “are we growing?” or “is it getting better?”, a line chart is the default. It handles new data well: each period adds a point, and the shape of the trend stays readable.

A few habits make trend charts robust:

• Fix the window. Show the last twelve weeks or the last thirteen months, not “everything since launch”. A rolling window keeps the chart the same size every edition.
• Show the same period last year as a second, lighter line when seasonality matters. It answers “is this normal for the time of year?” without extra commentary.
• Start the axis at zero for amounts such as revenue or orders, so small changes don’t look dramatic. Rates and percentages can use a tighter range, but label it clearly.

When the same trend also appears in a presented version of the report, line chart slides give it a layout with room for direct labels.

Use columns instead of a line when each period is a separate total that readers compare directly, such as monthly invoiced value. Keep to around twelve to fifteen columns; beyond that, switch to a line.

Progress against a target: bars with a marker

For “are we on target?”, show the actual and the target together. A horizontal bar for the actual, with a thin marker for the target, reads quickly and works whether the number is ahead or behind.

Avoid gauges and dials. They take a lot of space to show one number, and they are hard to compare side by side. A small table with actual, target and the gap often does the job better than any chart.

Breakdowns: sorted bars, not pies

For “which region is behind?” or “where does the revenue come from?”, use a horizontal bar chart sorted from largest to smallest. Long category names fit, the order shows the ranking, and new categories just add a row.

Pie charts struggle in recurring reports. They work only with a few slices of clearly different sizes, and the data rarely promises to stay that way. When a new product line or region appears, the pie gains a sliver nobody can read. If you must show share of a whole, a single stacked bar with three or four segments is easier to keep tidy.

Group the long tail. Show the top five or six categories by name and put the rest into “Other”. Decide the rule once, for example “top five by this month’s value”, so the chart doesn’t change shape for reasons unrelated to the business.

Change between periods: say it, then show it

Week-on-week changes are tempting to chart, but small numbers swing wildly and the chart becomes noisy. For most readers, a figure with its comparison beside it (“Orders 1,240, up 6% on last week”) does more than a chart of changes.

When you do chart change, use a column chart with a clear zero line, and colour increases and decreases consistently across every chart in the report.

Make every chart survive new data

A recurring chart will meet numbers you didn’t plan for. Before you settle on one, try it against awkward data:

1. A spike. Double one value. Does the rest of the chart flatten into nothing?
2. A new category. Add one. Does the legend still fit? Does the colour scheme have room?
3. A zero or a gap. Remove a week. Does the line break sensibly, or drop to zero misleadingly?
4. A long label. Rename a category to something twice as long. Does it overlap?

Charts that pass these tests can be left alone. Charts that fail need a fixed axis, a grouping rule or a different shape. It helps to set the chart up from a clean reporting table, as described in linking spreadsheet data to documents and slides, so the range a chart reads from grows in a predictable way.

Keep the set small and consistent

A recurring report needs fewer charts than people expect. Four or five, each answering a named question, are usually enough. Use the same colours for the same things throughout: one colour for actuals, one for targets, one for last year. Put each chart under a heading that states the question, and leave the answer to the commentary.

The KPI report templates piece shows where these charts sit in a weekly or monthly layout. Once the charts are chosen, the aim is not to touch them again for a quarter. A chart that readers recognise at a glance is worth more than a new one they have to learn.