The worst-case running time
of the Simplex method is
exponential !!!
Because the number of constraints
that you can formulate using
n variables
is exponential large
(one constraint can be formulated using one
subset
of the n variables --- you can have exponentially large
number of "corner" point
that the Simplex Method must visit...)
Real life problems:
The number of constraints used
to solve real life problems
are not expenentially large