The Census Bureau will announce later this month that the New York Congressional delegation will shrink to the smallest it has been in 200 years, continuing to erode the state's clout in Washington.The 435 seats in the House of Representatives are apportioned every decade on the basis of population. As a result of the steady tilt to the South and West, New York's 29-member delegation will lose at least one seat and possibly two, continuing an inexorable slide that began after World War II.