This is an excellent essay. You were able to convincingly present reasons for the radio station to reconsider its reformatting and also offered some food for thought regarding the pros and cons of the format change. There are some negligible grammatical errors that I need to point out in order to clean up the essay though.
To be properly substantiated to be considered convincing,
it is necessary to examine how big the newly arrived population
-...
the size of the newly...
If the increased number of people is substantial comparatively , it makes sense to focus the attention to those after retirement ,
- ...
to focus attention on the growing population of retirees ...
Moreover, how big is the population after retirement among the newly arrived population?
-
This is a redundancy since you already mentioned considering the population size earlier in the statement.Secondly
as to how big portion of they
- as to
what portion of their population ...
listen to radio
- listen to
the radio
the listeners'
music on radio.
- on
the radio
for previous prices for music CDs.
- prices
of music...
changes of rate of people
- changes
in the rate of people...
the format of radio.
- the format
of the radio station .
Lastly , it is
-
Finally ,
there is chance in breaking into this new market.
- a chance
of breaking into...
Further evidence needs to be provided in terms of the number and proportion of new population and those after retirement, listener's interest in listening to music or news through radio, and customer loyalty of those who listen to news.
- ... listen to news
before a solid, final decision about the change in radio station format is made.I really hope that my suggestions can help you further improve your essay. It is a very well written piece of work that you should be proud of :-)