A simple rule for aligning numbers

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I have recently been working with a client organisation which usually presented values in data tables centred within the columns.  This has prompted me to write this post.

The table below contains three alternative ways of presenting the same set of numbers:

justified

 

Right-justifying a column of numbers, as in Format 3, makes individual numbers easier to read and compare with others.  This is for the following reasons:

  • It is consistent with the way we were taught at school to lay out numbers for the purpose of adding them up or multiplying them.
  • We were taught to do this because right justifying numbers causes all the 1s, 10s, 100s, 1,000s etc to line up, as well as the thousand separator commas which make the numbers easier to read.
  • It makes large numbers stand out from the smaller numbers.  This effect is halved when numbers are centred, as in Format 2.
  • It emphasises the most important part of the number.  In Format 3, it is easy to see that the greatest income comes from Personal Loans, followed by Credit Cards.  In Format 1, the rightmost digits stick out which are the least important part of the number.

For these reasons, it is always best to present right-justified numbers to enable the audience to assimilate them rapidly.

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