I haven't noticed any difference between 70s and 80s. I have noticed a different between pre 70s and post 70s though. LR gets more convoluted via denser language and typical phrasings of answer choices are rehashed to say the same thing as they did in the older tests but in quite different ways. Strengthen and Weaken questions also get a lot softer in terms of how much they do for an argument. RC just gets slightly harder while LG has been fairly easy ever since the 40s. I think familiarizing yourself the wording especially of the LR sections of the 80s is the best approach, because LR fluency translates well in helping RC.
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I haven't noticed any difference between 70s and 80s. I have noticed a different between pre 70s and post 70s though. LR gets more convoluted via denser language and typical phrasings of answer choices are rehashed to say the same thing as they did in the older tests but in quite different ways. Strengthen and Weaken questions also get a lot softer in terms of how much they do for an argument. RC just gets slightly harder while LG has been fairly easy ever since the 40s. I think familiarizing yourself the wording especially of the LR sections of the 80s is the best approach, because LR fluency translates well in helping RC.