This should come as no surprise to anyone using a phone these days, but text messaging someone gets a far quicker response than voice mail. In a study by Sprint, those under the age of 30 are four times more likely to respond within minutes to an SMS than a voicemail, with roughly 91 percent responding within the hour. Adults 30 and older were twice as likely to text a reply within minutes rather than call.
In fact, the only people who tend not to reply in messaging form were those above the age of 65. I guess people under that age haven't gotten stuck in the habit of listening to a voice on the other line. I personally hate answering voice mails - very few people know how to be concise and clear on the phone, especially when they're essentially talking to themselves. Why listen to your friend Jane hem and haw about a good time to meet up when you could've spent three seconds reading "Im in da city. U free 2 meet?" [Wireless and Mobile News]