I'll try to make the structure clear by building it up from the core. I'll do a somewhat literal translation into English, note that this is NOT correct English. I'm not sure if this will help you, but I don't speak Chinese.
Der Abgang ist nicht so stark. = The (amount of) leaving isn't that strong.
Der Abgang in die Erwerbstätigkeit ist nicht so stark = The (amount of) leaving (it) into having a job isn't that strong.
Der Abgang in die Erwerbstätigkeit ist da nicht so stark. = The (amount of) leaving (it) into having a job, with respect to what has been discussed previously, isn't that strong.
Bei aller Initiative ist da der Abgang in die Erwerbstätigkeit nicht so stark. = Even considering everything those people start doing on their own, the (amount of) leaving (it) into having a job, with respect to what has been discussed previously, isn't that strong.
It would have been easier to explain this sentence if you had provided some context.