Devoted to the call center industry, the agents on the phones, and their managers

Brian Carroll cites a DMA report that the phone is the top tool in generating leads. 

According to the DMA study, "Telephone leads all media with the highest response rate of 5.53 percent."

Dimensional mail had a response rate of 5.28%

Email had an average response rate of 3.39%

Telemarketing has the highest response rate, but it is also the most expensive form of lead generation of the three listed.

Consider the following:

You might average 16 contacts in 1 telemarketing hour.

That telemarketing hour costs you $24

At  5% response rate, you get a lead per hour of 0.8.  That means that each lead cost you $30.

Compare this with a mail campaign.  To get a $30 lead with a direct mail campaign, you can spend up to $1.50 (that has to cover creative, printing, handling and postage).

(20 mail pieces generate 1 lead at 5%.  At $1.50 per mail piece, that lead costs you $30).

The real question is what leads convert better?