Here, we have a supply v/s demand situation.
Let us represent homeowners by 'O'
Let us represent renters by 'R'
15 years ago: (# of O) < (# of R)
Since then, Massive increase in #of R v/s relatively smaller increase in # of O
Hence, we can infer that the ratio of (# of R) to (# of O) has increased over the course of the last 15 years.
(D) highlights this perfectly. Hence,
(D) is the right answer.
The other answers are wrong for the following reasons:
A.
The number of renters is now lower than the number of homeowners. - Nope. The passage does not mention any information about exact number of home owners or renters. Hence,
eliminate (A)B.
Everyone who is a homeowner has rented at some time in the past. - The passage does not in any way suggest or describe the 'type' of people who used to rent homes. Hence,
eliminate (B). C.
The proportion of homeowners to renters has increased in the last fifteen years. - No. It is the exact opposite of what has actually happened. Hence,
eliminate (C).
E.
The proportion of homeowners to renters has not changed over the course of the previous fifteen years. - The passage certainly suggests that a change in proportion has occurred. Hence,
eliminate (E)