The most closely watched metric for Verizon Communications (VZ -2.51%) during earnings season isn't the company's revenue or profits. Instead, it tends to be its postpaid phone subscriber numbers. Postpaid subscribers have wireless plans that are billed monthly, as opposed to prepaid subscribers, who pay for their services upfront.Prepaid subscribers generally are not as affluent, and the business has much more churn. Meanwhile, its consumer and business wireline businesses are in decline. Broadband is a gr ...