There are a half-dozen subtle drivers of growth that account for the almost unbroken string of annual sales increases for the voluntary industry. These drivers propel industry sales ahead, even during weak economic times, and are in addition to the traditional "more people, selling more" momentum we have been chronicling for the last quarter of a century.

One of these drivers is the documented tendency of accounts, once they offer a voluntary benefit, to add a second, a third, (etc.) voluntary benefit in rapid succession. This serves as a built-in sales accelerator.

Once a broker sells an account on a voluntary offering, if she does a good job, she'll be rewarded with a string of new-product sales in the coming years. Looking at medium-size accounts that offer voluntary, as an example, 67 percent offer three or more voluntary products. That measure is 65 percent in large accounts and 74 percent in small accounts.