17. How to Design Tables

The first question is: Do you need a table? Tables are useful if repetitive data must be presented, and the precise values have importance. However, it is not good science to publish data just because you measured them. Printing a table is costly, and editors and reviewers scrutinise tables closely. Tables that have lots of standard conditions, lots of 0s, 100% or +/- s, or word lists, are usually not necessary.

Tables, just as figures, must also be self-explanatory: collectively, the title, table headings, and footnotes must allow the reader to understand the content of the table, without reference to the text.

Tables have a special format. The body of a table is organised into columns. There are no vertical lines, and only a few of the horizontal ones (see Box 12). The title of the table is always above the table itself. A horizontal line under this title separates it from the next element, the column heading. Below this, the body of the table is also separated from the parts above by a horizontal line. The end of the table is also marked by a horizontal line, separating the footnotes (if present) from the body of the table.

In the table heading, there can be partial horizontal lines, indicating sub-grouping. The extension of the horizontal line over certain columns indicates where the information above the line extends.

The organisation of the table is different from that of text. Table “lookup” is vertical, not horizontal: when we try to interpret a table, we look at columns first, so the numbers to be compared should be in the same column, not row. The tabulation of data follows the logic similar to figures: the independent variable should be on the left, and the dependent variable(s) on the right. Consider carefully, however, the organisation of the table itself. The table exists to present data; arranging a table according to the leftmost column — a common practice — may not be the best way (see Box 12). A marginal indicator in the manuscript helps you to see if you mentioned all of the tables in the text, in appropriate sequence. In the title, one may indicate the organisational principle of the data on the table itself.

Tables are often wider than necessary. Consider if all the information needs its own column, or whether some can be combined as in the table in Box 12. This could reduce the width of the table, and may allow the table to be printed in portrait rather than landscape orientation.

Footnotes can give additional information to help understand the table. They should be short and to the point.

Box 12. A sample table

Table 1 from Magura et al. (2010), https://doi.org/10.1111/j.1466-8238.2009.00499.x. © 2009 Blackwell Publishing Ltd. All rights reserved. Permission for further reuse must be obtained from the relevant holder of the exclusive rights.

This is Table 1 from Magura et al. (2010). Note that the information on the organisational logic of the table is included in the title. The column headings contain all information necessary to interpret the values in the body of the table, such as the measurement units. Where this is not possible or not easy (see the columns of rare and common species, for example, on the right of the table), footnotes are used. The two-level column headings allow some saving of space. On the leftmost column, the country and urbanisation stage were combined into one column, thus avoiding a repetitive column (writing out country names many times) and making the table narrower.