White space gives readers breaks between thoughts. These breaks give the eyes and brain a chance to rest. Studies have shown that readers comprehend text better when it includes more white space. In contrast, pages with large blocks of text can lull a reader to skimming, or dozing.
When you are writing a brief, give readers a new header at least every two or three pages. Give readers a new paragraph at least every one-half or two-thirds of a page. And, where possible, use short sentences.
Robert Dubose, Alexander Dubose Jones & Townsend LLP