A manual for writers of research papers, theses, and dissertations, 7th edition - Kate L. Turabian 2007

Column heads
Tables and figures
Part III. Style 20 spelling

A table must have at least two columns, each with a head or heading at the top that names the data in the column below.

Use noun phrases for column heads. Keep them short (or set them to wrap, as in tables 26.1 and 26.2) to avoid an excessively wide table.

Make column heads singular or plural depending on the data below. Stub heads, if present, are usually singular (see 26.2.5).

Capitalize column heads sentence style (see 22.3.1).

Align stub heads flush left; center other column heads over the widest entry in the column below. Align the bottom of all heads horizontally.

If your data are complex, you may need to include special types of heads in addition to the column heads. Such a head may apply to two or more columns of data. Center the head over the relevant columns with a partial-width horizontal rule beneath (and, if necessary, above) it. Table 26.2 shows heads both above (“1950”) and below (“Provincial Assembly”) the column heads.

Heads may have explanatory tags to clarify or to indicate the unit of measure for data in the column below. Enclose such tags in parentheses. You may use abbreviations and symbols for such tags (mpg, km, lb., %, $M, and so on), but be consistent within and among your tables.

Responses (%)

Pesos (millions)