Question

<!-==text==begin==-> I have some difficultiesusing Present Perfect and Simple Present.
So inthis sentence: Things have changed a great deal atColtech, Inc. When we first started working herethree years ago, the company only had sixemployees. Since then, we (expanded or haveexpanded ???) to include more than 2000 fulltimeworkers.
Is it possible to use either ofthem or just one of them? If just one why can’t Iuse the other?
Thanks!
June  

Replies:
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My choice would be: "Since then, we have expanded to…"

Though the action (expansion of the work force) has been done in the past, the action still has a direct relationship to the present time (Since then…); therefore I think the preferred choice here is the Present Perfect.

If the past action had a relationship to a specific time in the past, we then use the Past Perfect. For example: After we had expanded our staff to over 2000 workers, we were told not to recruit any more.

Did you mean Present Perfect and Simple PAST?
SIMPLE PAST says WHEN
” I SAW John YESTERDAY. (WHEN?-YESTERDAY)”
PERFECT PRESENT doesn’t say when but what has happened BEFORE the time of speaking (with time words like SINCE, ALREADY, BEFORE, YET, EVER, NEVER)
“I HAVEN’T SEEN John SINCE yesterday.”
“I have been to the USA before ”
“I’ve done my homework already.”