Avoid setting headlines, or extended text, entirely in upper case type. Headlines set entirely in upper case (capital letters) are harder to read and take up more space than headlines set in both upper and lower case characters.

Words set in upper case type are harder to read than words set in lower case type because readers are assisted by character and word shapes to understand their meaning. Words set in lower case characters are easier to recognize because of their distinctive shapes, created by descenders (portions of the letters below the baseline) and ascenders (upward-reaching characters).

Words set entirely in upper case type also occupy up to thirty percent more space. Awkward character spacing can appear when upper case characters appear next to each other, so you need to pay attention to character spacing when using all capital letters.