It also shrinks your reachable market by about 40%, and drops your conversion rate enough to wreck your CAC and cost per outcome.
If someone told you parallel dialing doesn't hurt performance, they either haven't looked at the data or they're selling you something.
Only 20% percent of your market will ever answer a cold call. Parallel dialing cuts that down to twelve.
When phone is by far the highest impact, fastest-to-result sales channel there is, that result from a parallel dialer means you're not moving faster. You're just eliminating conversations you could have had.
When you dial properly and know who you should call, it has a dramatic impact on everything: your costs, your scale, your ramp, and your ability to reach the prospects who would have picked up.
Volume is vanity. The data's in. Watch the math.