Rule: When equivalent items are compared, the first item is introduced by as (or so) and the second element by as.
Examples of errors:
(1) Prices for exports did not rise that much as those for imports.
(2) Then the tribe starts going the same way than all civilized societies.
(3) My mother seemed not so happy than I was.
(4) If I'm so close to somebody like you are to Rachel I have to tell the person the truth.
(5) His legs are such as long as yours.
(6) In Italy the number of illegal abortions is about as 10 times as high.
The comparison of equivalent items is accomplished with the structure as...as. The alternative structure so...as is used only in negative sentences and in formal style. In the case of what one might call multiple or fractional equivalence (of. (6)), the first element of the comparison is modified by a numerical expression:
My house is one-third/half/twice three times as big as his.
As in other comparative structures, the second element may be omitted when context allows--as in (6), the full version of which would be
In Italy the number of illegal abortions is about 10 times as high as (it is) in Germany.