Columns of figures should be tabular and right aligned if they share the same unit, and the headings should match.
Guidelines, via Morten Hjerde (IXDA thread):
- All text left aligned
- All numbers right aligned
- Single characters are centered
- Numbers that are not values, like product codes for example, are treated
like text and left aligned.
- Use the same number of decimal places for all numbers in a column
- Left align dates.
- Use 2 digits and leading zero for day numbers (this may be cultural?), and use
the same format for dates throughout
I'm not able to find any Tufte-esque references, but plenty of examples:
I had to take out additional links and images because I don't have the rep yet. Sorry friend :\
Hoefler & Frere-Jones, without going into the HCI justification, provide a reasonable example (source):
Example two, pulled from this Behance profile. Just clear enough to tell what's going on: