Improving Tables

1. Problem Statement

Tables and graphs are the two main approaches we have to communicate quantitative information. They both have different roles: tables are usually best suited to displaying information where we want to look up individual values and compare individual values. Precise values are usually shown. Graphs, on the other hand, are best suited to showing trends where the message is contained in the shape of the values, eg, showing patterns over time.

The merit of tables or graphs for different visualisations is covered extensively in data visualisation literature – see some suggestions on our “Resources that helped us” tab – and won’t be mentioned further here.

Much focus in data visualisation is on graphs or info-graphics. Much less discussion is centred on the humble table perhaps because they are overly familiar and we have an assumption, considered or not, that the default Word “gridline” table is “good enough”. However, as this blog post will show, well thought out and formatted tables can greatly improve the clarity and therefore impact of your message.

2. Suggested Approach and Commentary

This post assumes that we have chosen a table as our means of visualisation. Straightforward table design decisions include:

1. Delineating columns and rows; 
2. Arranging data;
3. Formatting text;
4. Summarising values;
5. Page information; and
6. Additional table characteristics

The rest of this section discusses each of these features in turn.


There is good discussion on all aspects of table design in Stephen Few’s book, Show Me the Numbers (Designing Tables and Graphs to Enlighten) – see our Resources page linked above. 

First, a standard Word or PowerPoint approach via (Insert > Table).  What is presented is a straightforward “grid” where the gridlines have been highlighted for emphasis.  In fact, the grid itself gets too much attention and detract from the information in the table. Few of us ever go much beyond amending this default view and yet there are compelling reasons to do so as the rest of this blog post will illustrate. 

This brings us to our first point.

  

2.1 Delineating columns and rows

In general, removing gridlines and replacing them with white space can dramatically improve the effectiveness of a table.  In general, the fewer gridlines the better, meaning there is less clutter for the reader to work through to understand the content in the table.  Individual data items are found more easily. 

Experiment with the amount of white space but don’t add too much.  Notice the difference between the table presentations below which experiment with white space, rules and fill color to highlight particular cell values.

Notice the difference in clarity between A) and then to D).  In A) table cells appear to be equally important.  In D) we have helped the reader focus straightaway on the most important cell(s).

In large tables with many rows, highlighting alternate rows can greatly help the reader scan across the table to pick out values of interest.  See the example below where a pale background fill has been applied to alternate rows.  Alternatively, or in addition, you can use a blank row and column after every (say) fifth row/column to help guide the reader.

Scanning along the row for Product 6, for example, is a lot easier than if no fill had been applied to the table. 

2.2 Arranging data

How do we best arrange data in a table to tell its story?  Western convention is that time-series data works best from left to right, eg columns headed Q1 2018, Q2 2018… Q4 2018 working from left to right across the table.  Equally, columns that show data values derived from another column should be placed to the right of that column to ensure a logical data flow when reading the table left to right. 

If we want to display a ranking arrangement, it usually works best to display items vertically from largest at top to smallest at bottom.   Some examples are given below:

The tables above show conventional time order left to right (Q1, Q2, Q3, Q4).  In the lower example, columns are clearly grouped as "2018 Sales by quarter", plus the units (£m) are shown only once, rather than four times, which is also helpful.

2.3 Formatting text

Western convention is to prefer horizontal orientation, unless reasons of space force us to do otherwise, eg a table with many columns might justify vertically-orientated column headers. 

Text should be aligned to the left and numbers aligned to the right.  Columns that contain simple Y/N text, for example, work well when centred in a column. 

Some examples are shown below: 

In A) the first column of text is left-aligned and the numbers in the second column are aligned to the right.  In B) the text in the second column are centred.

Fonts – Choose a font that is as legible as possible.  The same font should be used throughout a table.  Each numeric digit (0-9) should have the same width to enable numbers to align within a column.  Good choices of font are Arial (the font used in this post) or Times New Roman. 

2.4 Summarising values

Column and row summaries can be very helpful to avoid the reader mentally needing to, or attempting to, add up row or column totals themselves.  Consider making them visually distinct from the regular columns, eg through use of bold formatting.  An example is shown below:

2.5 Page information

Table title and sub-title: A clear table title helps anchor your table within the document and means its content can be unambiguously referred to at a later date.  For example, a title might be:

2019 Q3-to-date regional sales (as at 25/08/19)

If this table is referred to at a later date, the reader will have no problem understanding what the table is showing.  As a general principle, the aim should be to limit the possibility that the reader needs to ask follow-up questions. For example, in the above table, if “sales” could mean any of “booked orders”, “delivered orders” or “payments received”, the title could be improved further to clarify which measure is being reported.

2.6 Additional table characteristics

Repeat column headers at the top of each page

This is particularly valuable when a long table breaks across one or more pages of a report.  If the column header repeats at the top of each page then the user doesn’t need to refer back to the very top of the table, on the preceding page or even further back, for the column headers.  Instructions to do this in Word are as follows:

3. Applicability and Alternatives

This blog post assumes that a Table is our preferred means of visualisation – no alternatives were considered.

4. Implementation

All tables presented in this post have been created in Excel 2010 but will work in any version of Excel.

5. Context

Tables are ubiquitous in printed reports.  Few of us go beyond making simple changes to the default Word or PowerPoint default “grid view” table.  This post has shown that straightforward changes such as removing gridlines and replacing with whitespace, and thinking about row and column order and alignment can greatly improve the readability of your tables and hence the impact they make on your audience.