ANALYZE THE STIMULUS:
Fact 1: In 1984, network television commercials accounted for 80% of all network and non-network television advertising revenue.
Fact 2: In 2004, that figure was 60%.
Fact 3: During that same period, operating cost for the networks remained steady,
Fact 4: In 2004 every major network announced record setting profits.

Question: The information above, if true, supports which of the following conclusions?

Pre-thinking:
- From fact 3: Costs remained;
- From fact 4: In 2004, Network TV had profits --> REVENUE - COST >= 0--> Revenue must be equal or greater than that in 1984. KEY. We don’t have to assume revenues will be equal or greater, this is the hidden fact.
- Clearly, revenue of Network TV increased (or stayed the same) but its percentage decreased compared to Non-network TV. Thus, non-network TV must grow at faster rate than network TV in terms of revenue.

ANALYZE EACH OPTION:

A) Between 1984 and 2004, the number of homes with access to non-network television channels increased by more than 20%.
Wrong. We can’t infer “20%”.

B) Teenagers comprise a growing proportion of television viewers, and teenagers prefer to watch non-network television shows.
Wrong. Teenagers are only a sub-group. It can't represent for the whole group.

C) The amount of advertising revenue earned from non-network television commercials in 2004 was greater than the amount of revenue earned by network television commercials in 1984.
Wrong. NOTE: we can’t convert from percentage to absolute value. This is a popular trap in GMAT. Larger percentage does not mean larger absolute value and vice versa.

D) Between 1984 and 2004, advertising revenue earned from non-network television commercials grew at a faster rate than revenue earned from network television commercials.
Correct. KEY is revenue of network TV increased but its percentage decrease, thus it must grow at slower rate than non-network TV did.

E) Soon revenue from non-network television commercials will surpass revenue from network television commercials.
Wrong. Can’t infer that.

Answer: D