In my opinion,economy should be taught.
Why is it not included?
The first reason is there are not many people who can teach. Some people have knowledge to share , but they don’t want to do because if they share the idea, people would follow, demand would boost up and they have to change the way to earn money.
Additionally they know what they have to spend time to. Actually it is not for education.
The second reason is that if people get proper education, some companies could go bankrupt.
They just advertise something good for people, but if you have knowledge, you can analyze and search based on proper information.
On the other hand, if people have proper knowledge, some doubtful companies would have gone.
Paragraph beginning, “The second reason…”
“They advertise [that] something [is] good for people, but, if [people] have knowledge, [they] can…”
This does not seem to be a separate reason, but a continuation of the previous reason of guarding the information so they can continue the status quo. I might suggest the following: “A population adequately educated in economics could cause some companies to go bankrupt. If they advertise that something is good for people, but the people use economics to analyze and properly research the data in the advertisement, the company could lose money.”
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Paragraph beginning: “On the other hand…”
“...people have proper [economic] knowledge, some [dubious] companies would (might?) (either “be gone” or, stronger, “close their doors”).”
This does not seem to be “on the other hand” (contradictory to the previous point), but a continuation of it. Instead of starting a short, new paragraph, you could append a sentence onto the last paragraph: “A public educated in economics could lead to the closure of more dubious companies.”
Great job!