well it kind of depends on a few things.
are you calling out and answering calls on a crowded channel like 38LSB?
if so, then you can be sure that for every person you hear booming through your radio, there are 10-100 people in your regional area that are also trying to answer that person.
you won't hear any of these people because they are not in your skip zone.
they are too far from you to hear, but too close for your signal to hop to them.
if you are operating at a level of 50 watts or less, and your antenna is just a vertical on a 20 foot mast, then your chances of being the one who gets their numbers called out by the DX station are not going to be great.
people tend to answer the person who comes into their radio the strongest because that person is better equipped to carry on a full QSO than someone who can be heard but keeps getting covered up by other stations trying to jump in.
get a station that can do 400 watts PEP and get the base of your antenna up to the 50 foot level and everything changes.
with a modest station and a crowded channel, your best bet is to only try to answer stations that hit you at like +30 or "in the red" on your meter.
chances are you will hit them with about the same signal strength.
if you are sitting on an empty channel calling CQ, then you just have to be patient and keep on calling because eventually someone will be spinning the dial past you and we all love to make contacts on empty channels.
hope this helps.