Writing: The Odd Thing About Even Numbers

A nifty copywriting rule to remember is to always use odd numbers. For some reason, even numbers are not as effective as odd ones in copy.
An example of this is, “The Six Energy Stocks You Must Own Now” is somehow less appealing than “The 5 Energy Stocks You Must Own Now” even though it promises an extra stock recommendation. And you almost never see a book titled “100 Ways to do X.” It’s almost always “101 Ways.”
Copywriter Gymi Slezinger has a theory about this. “Even numbers have balance and closure,” says Gymi. “They don’t need you. Odd numbers have something hanging. There is an urgency in them.”
One exception to the rule: 10 works very well in copy. For example, “10 Tips for Better Technical Writing,” because, according to Gymi, it is authoritative.