Originally Posted By: NYSteve
TV guy here...
Linear TV ad inventory is broken up by what we call 'avails' across broadcast and cable networks. Assume there are 17minutes of commercials per hour.
For broadcast stations (ABC, NBC, etc) the national network has majority of the inventory, say 15 minutes or 30 commercials per hour. They sell these to national advertisers such as pharma companies or really fortune 500. Since the networks also distribute content they air, they try to sell demographics of a particular show, usually based on age and gender. For local news, it is usually an 55+ skew to the viewers, hence the prevalence of pharma commercials.
The remaining 2minutes (or whatver it actually is) goes to the local broadcast station. They sell to local businesses within the geographic market - HVAC, lawyers, restaurants, etc. That is because the local companies can't afford and also dont want to buy the whole country on ABC, just their ABC station in their market.
There is a similar breakout with the cable networks, except the 2minutes per hour go to the cable/satellite/telco distributor (Comcast, Verizon, Dish, etc). So they have 2min per hour across ~50 or networks every hour. Also why you might see a national Ford Truck commercial on Discovery and also one for Bill's Ford Dealership down the road.
Will answer any questions that I'm allowed to...
PS - I don't create the commercials, flame the creatives for what you see
The few times I watched Jerry Springer, most commercials seemed local. Commercials aimed towards the 20 something age bracket that drooped out of high school.