Student or Learner
Would you say that these two sentences have the same meaning?
Studies reveal that expenditures for sport increase in proportion to available income.
Studies reveal that expenditures for sport increase as does available income.
The paraphrase in the second sentence inadvertently used a clause -- and that severed the proportion relationship.
Instead, it makes two unrelated claims:
1) expenditures for sports increase
2) and income increases too
The difficulty is that the expression "as" does have a use in statements of proportion:
As this, so that
A is to B as B is to C
"Studies reveal that expenditures for sports increase as available income increases" is the way to phrase this relationship.
You can even maintain this statement of relationship by saying, "Studies reveal that expenditures for sports increase as available income does."
But you lose the relationship by transferring the word "does' to the beginning of the phrase:
"Expenditures for sports increase, as does available income" is the same as saying
"Kodiak bears live year-round in the Arctic, as do polar bears."
It becomes just a remark about two non-dependent phenomena.
But even so, the first sentence is better because by specifying "in proportion," it specifies not only that the two increases are simultaneous and dependent, but also that the amount of increase in one is of the same relative magnitude as the increase in the other. If available income increases by 10%, then expenditures for sports increase by 10% too.
I tend to write "Thanks" at the bottom of my posts; I didn't know it was expected of me to thank each respondent personally (I certainly don't expect others to thank me for my replies if they are helpful). It is however not true that I "never" thank a respondent - I do when I feel that the respondent has invested a certain amount of time and effort in his reply.
Ms Phorn and some others are so conscientious about giving people a click that it is a joy to respond to them.
Anyway, I hope you found my post useful, and "Thanks!" for the click!