Circle Line's ridership figure is even worst than NEL when it
started on a per km basis. Anyway Circle Line started only on May
28 2009, so it has negligible impact on the NSL/ EWL/ NEL ridership
over the past 2 years.
In fact Circle Line ridership figure would be slave from NEL,
EWL & NSL.. it's the other way round
for now i would agree with you on this point but once the stage1
and 2 are runniing, we might see a reverse in the trend in your
last sentence though i cannot comfirm it, based on the location of
the stations near the CBD area and marina area, those are likely to
have high human traffic which itself might surpass the NEL.
another fact: i believe you also did not take into account on 1
station which is part of circle line and NSL-Doby ghaut <- this
is the key station which is the merging of all 3 lines which 2/3 of
it is already operated by SMRT, thus it would also affect the
upcoming data when it opens with Stage 1 and 2
these are just my estimates though.