  Both parties now agree that we don't have extra budget money
lying around, but both say government does need to spend more on
"infrastructure."  Even conservatives want more spent on roads
and mass transit.  The reason, advocates claim, is that
infrastructure, unlike most government spending, has a
"multiplier effect" -- it creates new wealth by doing things
like speeding up travel.  Well, it might.  Advocates also point
out something that seems obvious to them: Infrastructure is a
job that must be done by government. Who else would launch big
projects like the New York City subway system? Subways are what
Big Government supporters call a "public good."  They are
important to many people, but there's no way that business would
build subways or run them, they argue. Subways lose billions of
dollars. Entrepreneurs would never invest in subway cars or dig
subway tunnels -- there's no profit in that.  But often what we
"obviously know" ... is not so.  Most of New York's subways were
actually built by private co