Confused about the usage of present perfect tense

Question

My problem is whether present prefect tense means that the result of a past action still exists or it means that the action itself is still happening or still important. When I say "I've lost my book" it means the results of the "losing action" still important currently. But it does not mean I am losing my book every moment, and this will be good tragic science fiction movie related to space black hole or something.

Context: The development is the media spreading more news about crime.

This development makes people feel unsafe for psychological reasons, and they may falsely think that crime rates were\ have increased.

Using "were" means that:

• crime rates was increased is the past.

• the rates went for example from 5 to 8; however, it is not increasing anymore.

Using "have" means that:

• crime rates were increased in the past.

• the rates went for example from 5 to 8; however, it is not increasing anymore because present perfect tense applies to the result of an action not the action itself.

If this was right, and I don't know whether I got it right or not, then why native English speakers prefer to use "have" in this case, it is completely useless!

When Australia has applied the economic policies which I mentioned earlier, according to the government statistics, most employees found a new job in supermarkets after their former employer companies had been closed.

The content is kind of silly, but please ignore this for now :) This one is also problematic because an English teacher decided that "has" is wrong. When I wrote "has" I wanted to emphasis that "economic policies" are still applied today, and in my opinion, using past tense is wrong because it this context it is not clear whether "economic policies" are still there or rolled back.

So where is my misunderstanding regarding present perfect tense?

Answer 1

Present perfect form marks events in the past that have an important effect in the present.

It applies both to actions that are complete or incomplete.

The choice of whether use perfect form is not one of grammar but meaning. Two speakers may make different choices depending on whether each believes some effect is important or not important.

In the case of "crime rates were increased" versus "crime rates have increased", the difference is not whether the rates continue to increase, but of whether the increase has an important effect on the present. The topic of discussion is the present feeling of fear, which is an important effect from the increase. The latter choice, the present perfect, is better, because it emphasizes the relationship between the increase and the fear.

Answer 2

If crime rates were increased, it means they were increased by someone or something. That is passive voice, which is not what you mean, I think. So just use "increased" if it, the action, happened in the past. The present perfect is used when the present result of a past action is emphasized, it is the present result that is important, not the past action itself. If you want to express something started in the past and is still going on, use present perfect continuous: have been increasing, here the action is ongoing.