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Computing Congressional Apportionment

Since that first census in 1790, five methods of apportionment have been used. The current method used, the Method of Equal Proportions, was adopted by congress in 1941 following the census of 1940. This method assigns seats in the House of Representatives according to a "priority" value. The priority value is determined by multiplying the population of a state by a "multiplier."

For example, following Census 2000, each of the 50 states was given one seat out of the current total of 435. The next, or 51st seat, went to the state with the highest priority value and thus became that state's second seat. This continued until all 435 seats had been assigned to a state. This is how it is done.

Equal Proportions Method

P - represents a state's total population

n - represents the number of seats a state would have if it gained a seat (because all states automatically received one seat the next seat gained is "seat two," and the next "seat three," and the next "seat four," and so on.)

The multiplier equals:

Mathematical Expression: 1 / square root of (n * (n-1))

Additional Congressional Seats Awarded to Massachusetts using the Equal Proportions Method

Additional Seat

Seat #

Priority Value

2

80

4638368.755

3

124

2677963.449

4

172

1893606.115

5

215

1466780.989

6

261

1197621.663

7

311

1012175.044

8

355

876569.301

9

402

773061.4591

 


Ranking of States for the last Congressional Seat

The US Census Bureau announced on December 21, 2010 that Massachusetts will lose a congressional seat due to re-apportionment based on the 2010 Census.  Minnesota was awarded the 435th seat in Congress. 

Rank

State

2010 Population (Military and Overseas included)

Members of Congress if awarded the 435th Congressional Seat

Additional Population needed to be awarded the last seat

1

Minnesota

5,314,879

8

0

2

North Carolina

9,565,781

14

15,753

3

Missouri

6,011,478

9

15,028

4

New York

19,421,055

28

107,057

5

New Jersey

8,807,501

13

63,276

6

Montana

994,416

2

10,002

7

Louisiana

4,553,962

7

48,858

8

Oregon

3,848,606

6

41,487

9

Ohio

11,568,495

17

144,928

10

Virginia

8,037,736

12

122,192

11

California

37,341,989

54

653,688

12

Illinois

12,864,380

19

270,086

13

Texas

25,268,418

37

652,566

14

Massachusetts

6,559,644

10

178,195

Congressional re-apportionment factors in military and overseas citizens claiming Massachusetts residence.  The Massachusetts in-state resident population of 6,547,629 is used for redistricting.

To learn how Congressional Seats are awarded please visit:  U.S. Census Bureau: Computing Apportionment

 


History of Massachusetts Membership in the United States House of Representatives

Members of Congress from Massachusetts

Census

Year

Members

Initial Apportionment 1

1789

8

1st Census

1790

14

2nd Census

1800

17

3rd Census 2

1810

20

4th Census

1820

13

5th Census

1830

12

6th Census

1840

10

7th Census

1850

11

8th Census

1860

10

9th Census

1870

11

10th Census

1880

12

11th Census

1890

13

12th Census

1900

14

13th Census

1910

16

14th Census 3

1920

16

15th Census

1930

15

16th Census 4

1940

14

17th Census

1950

14

18th Census

1960

12

19th Census

1970

12

20th Census

1980

11

21st Census

1990

10

22nd Census

2000

10

23rd Census

2010

9

1. No change was made after the 14th Census (1920), as Congress could not agree on a method for apportionment.

2. Formerly part of Massachusetts, when Maine achieved statehood in 1820, Congress assigned the new state one At-Large Representative, leaving Massachusetts with its allotted 20 Representatives. In the 17th Congress (1821–1823), the final Congress before the apportionment following the 4th Census (1820), Congress reassigned seven Massachusetts Representatives to Maine, leaving Massachusetts with 13 Members of the House.

3. Constitutional Apportionment (Article 1, Section 2).

4. The current method of apportionment began following the 1940 Census

Source: Office of the Clerk, House History: Congressional Apportionment


For more information on Congressional Apportionment please visit:

Office of the Clerk, U.S. House of Representatives: Congressional Apportionment

U.S. Census Bureau, Congressional Apportionment: Related Sites

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