United States congressional apportionment

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Allocation of congressional districts after the 2000 census.

United States congressional apportionment is the redistribution of the 435 seats in the United States House of Representatives among the 50 states in consequence of the constitutionally mandated decennial census. Each state is apportioned a number of seats which approximately corresponds to its share of the aggregate population of the 50 states (populations of Washington, D.C. and federal territories are not included in this figure). However, every state is constitutionally guaranteed at least one seat.

The decennial apportionment also determines the size of each state's representation in the United States Electoral College—any state's number of electors equals the size of its total congressional delegation (i.e., House seat(s) plus Senate seats).

Federal law requires the Clerk of the House to notify each state government of its entitled number of seats no later than January 25 of the year immediately following the census. After seats have been reapportioned, each state determines the boundaries of Congressional districts—geographical areas within the state of approximately equal population—in a process called redistricting.

1 House size
2 Apportionment methods
- 2.1 The Equal Proportions Method
3 Past apportionments
4 Projected changes following the 2010 census
5 Notes
6 See also
7 External links

[edit] House size

Ratio of representation in the House, 1789–1923
Years	Source	Constituents per Representative
1789–1793	U.S. Constitution	30,000
1793–1803	U.S. Census of 1790	30,000
1803–1813	U.S. Census of 1800	33,000
1813–1823	U.S. Census of 1810	35,000
1823–1833	U.S. Census of 1820	40,000
1833–1843	U.S. Census of 1830	47,700
1843–1853	U.S. Census of 1840	70,680
1853–1863	U.S. Census of 1850	93,425
1863–1873	U.S. Census of 1860	127,381
1873–1883	U.S. Census of 1870	131,425
1883–1893	U.S. Census of 1880	151,912
1893–1903	U.S. Census of 1890	173,901
1903–1913	U.S. Census of 1900	194,182
1913–1923	U.S. Census of 1910	212,407

The United States Constitution requires that

The number of Representatives shall not exceed one for every thirty thousand, but each state shall have at least one Representative (Article I, Section 2, Paragraph 3)

Prior to the twentieth century, the number of representatives increased every decade as more states joined the union, and the population increased.

In 1911, Public Law 62-5 set the membership of the U.S. House at 433; with the subsequent admission of Arizona and New Mexico as states, membership increased to 435, where it has remained (except for a brief period from 1959 to 1963 following the admission of Alaska and Hawaii, during which House membership was 437). If the ratio as specified by the Constitution of one representative for every 30,000 people were maintained today, the House of Representatives would have about 10,000 members. Instead, today one member represents about 650,000 people, which varies by state.

Proposals have been made to add voting representation for the District of Columbia, now represented only by a non-voting delegate, who is not counted as one of the 435 House representatives. A recent bill, the District of Columbia House Voting Rights Act of 2007, if passed, would resolve the issue by permanently increasing House membership to 437. One of the new members would be from the District of Columbia; the other would be from the next state in line to receive another House seat (as described below), presently Utah. The political appeal of this plan lies in its balancing of a new, presumably Democratic seat (D.C.) with a new likely Republican seat (Utah).

[edit] Apportionment methods

Apart from the fact that the number of delegates is at least 1 for each state, as required by the Constitution, a state's number of representatives is in principle proportional to population (thus equalizing the size of congressional districts nationwide). No method of calculating this desired result, however, has been found perfectly satisfactory in practice. Five distinct methods have been used since the adoption of the Constitution, all of them susceptible to mathematical paradoxes.

[edit] The Equal Proportions Method

Further information: Huntington-Hill method

The so called "Equal Proportions method" is the apportionment methodology currently used.^[1] The method derives its name from the fact that it guarantees the property that no additional transfer of a seat (from one state to another) will reduce the percentage difference in per capita representation.

In this method, as a first step, each state is automatically guaranteed at least one seat in Congress. That means there are a total of 385 seats left to assign.

The remaining seats are assigned one at a time, to the state that "deserves" another seat the most. Thus, the 51st seat always goes to the most populous state (currently California).

The apportionment method uses a mathematical formula to express the priority ordering of states for an additional seat. For instance, in the example above, California has already received a second seat and thus "deserves" a third one less.

The formula used by the method of equal proportions is

$A=\frac{P}{\sqrt{n(n+1)}}$

where P is the population of the state, and n is the number of seats it currently has. An equivalent, recursive definition is

$A_{n}=(A_{n-1})(\frac{n}{n+2})^{-\frac{1}{2}}$

where n is still the number of seats the state has, and for n = 1, A is explicitly defined as

$A_{1}=\frac{P}{\sqrt{2}}$

A sequential definition may likewise be given where the n = 1 case is defined as above, but the formula is

$A_{n+1}=(A_{n})(\frac{n-1}{n+1})^{-\frac{1}{2}}$

When all states have 1 seat, the largest value of A corresponds to the largest state. But now that California has 2 seats, its priority value decreases, and it has to take a step back in line. The 52nd seat goes to Texas, the 2nd largest state, but the 53rd goes back to California, and so on until all the seats have been handed out. Each time a state gets a seat, its priority drops and another state comes to the top of the list.

The Census 2000 Ranking of Priority Values^[2] shows the order in which seats 51–435 were apportioned after the 2000 Census, with additional listings for the next five priorities. North Carolina was allocated the final (435th) seat. Utah (priority list 436) missed a fourth seat by only 857 residents. Legal action by Utah to amend the results, citing irregularities in the North Carolina count and undercounting of Utah's overseas missionary population (suggested to be as many as 14,000), was unsuccessful. However, Utah would have received a fourth seat if the District of Columbia House Voting Rights Act of 2007 had passed.

[edit] Past apportionments

See also: Apportionment Bill

Note: The first apportionment was authorized by the Constitution, not the Census.

Census	Year	Size	AL	AK	AZ	AR	CA	CO	CT	DE	FL	GA	HI	ID	IL	IN	IA	KS	KY	LA	ME	MD	MA	MI	MN	MS	MO	MT	NE	NV	NH	NJ	NM	NY	NC	ND	OH	OK	OR	PA	RI	SC	SD	TN	TX	UT	VT	VA	WA	WV	WI	WY
Const.	1789	65	-	-	-	-	-	-	5	1	-	3	-	-	-	-	-	-	-	-	-	6	8	-	-	-	-	-	-	-	3	4	-	6	5	-	-	-	-	8	1	5	-	-	-	-	-	10	-	-	-	-
1st	1793	105	-	-	-	-	-	-	7	1	-	2	-	-	-	-	-	-	2	-	-	8	14	-	-	-	-	-	-	-	4	5	-	10	10	-	-	-	-	13	2	6	-	-	-	-	2	19	-	-	-	-
2nd	1803	142	-	-	-	-	-	-	7	1	-	4	-	-	-	-	-	-	6	-	-	9	17	-	-	-	-	-	-	-	5	6	-	17	12	-	1	-	-	18	2	8	-	3	-	-	4	22	-	-	-	-
3rd	1813	182	-	-	-	-	-	-	7	2	-	6	-	-	-	-	-	-	10	1	-	9	20	-	-	-	-	-	-	-	6	6	-	27	13	-	6	-	-	23	2	9	-	6	-	-	6	23	-	-	-	-
4th	1823	213	3	-	-	-	-	-	6	1	-	7	-	-	1	3	-	-	12	3	7	9	13	-	-	1	1	-	-	-	6	6	-	34	13	-	14	-	-	26	2	9	-	9	-	-	5	22	-	-	-	-
5th	1833	240	5	-	-	-	-	-	6	1	-	9	-	-	3	7	-	-	13	3	8	8	12	-	-	2	2	-	-	-	5	6	-	40	13	-	19	-	-	28	2	9	-	13	-	-	5	21	-	-	-	-
6th	1843	223	7	-	-	1	-	-	4	1	-	8	-	-	7	10	-	-	10	4	7	6	10	3	-	4	5	-	-	-	4	5	-	34	9	-	21	-	-	24	2	7	-	11	-	-	4	15	-	-	-	-
7th	1853	234	7	-	-	2	2	-	4	1	1	8	-	-	9	11	2	-	10	4	6	6	11	4	-	5	7	-	-	-	3	5	-	33	8	-	21	-	-	25	2	6	-	10	2	-	3	13	-	-	3	-
8th	1863	238	6	-	-	3	3	-	4	1	1	7	-	-	14	11	6	1	9	5	5	5	10	6	2	5	9	-	-	-	3	5	-	31	7	-	19	-	1	24	2	4	-	8	4	-	3	11	-	-	6	-
9th	1873	292	8	-	-	4	4	-	4	1	2	9	-	-	19	13	9	3	10	6	5	6	11	9	3	6	13	-	1	1	3	7	-	33	8	-	20	-	1	27	2	5	-	10	6	-	3	9	-	3	8	-
10th	1883	325	8	-	-	5	6	1	4	1	2	10	-	-	20	13	11	7	11	6	4	6	12	11	5	7	14	-	3	1	2	7	-	34	9	-	21	-	1	28	2	7	-	10	11	-	2	10	-	4	9	-
11th	1893	356	9	-	-	6	7	2	4	1	2	11	-	1	22	13	11	8	11	6	4	6	13	12	7	7	15	1	6	1	2	8	-	34	9	1	21	-	2	30	2	7	2	10	13	-	2	10	2	4	10	1
Census	Year	Size	AL	AK	AZ	AR	CA	CO	CT	DE	FL	GA	HI	ID	IL	IN	IA	KS	KY	LA	ME	MD	MA	MI	MN	MS	MO	MT	NE	NV	NH	NJ	NM	NY	NC	ND	OH	OK	OR	PA	RI	SC	SD	TN	TX	UT	VT	VA	WA	WV	WI	WY
12th	1903	386	9	-	-	7	8	3	5	1	3	11	-	1	25	13	11	8	11	7	4	6	14	12	9	8	16	1	6	1	2	10	-	37	10	2	21	-	2	32	2	7	2	10	16	1	2	10	3	5	11	1
13th	1913	435	10	-	1	7	11	4	5	1	4	12	-	2	27	13	11	8	11	8	4	6	16	13	10	8	16	2	6	1	2	12	1	43	10	3	22	8	3	36	3	7	3	10	18	2	2	10	5	6	11	1
14th	1923	435	No apportionment enacted. Distribution of seats from 1913 unconstitutionally remained in effect.
15th	1933	435	9	-	1	7	20	4	6	1	5	10	-	2	27	12	9	7	9	8	3	6	15	17	9	7	13	2	5	1	2	14	1	45	11	2	24	9	3	34	2	6	2	9	21	2	1	9	6	6	10	1
16th	1943	435	9	-	2	7	23	4	6	1	6	10	-	2	26	11	8	6	9	8	3	6	14	17	9	7	13	2	4	1	2	14	2	45	12	2	23	8	4	33	2	6	2	10	21	2	1	9	6	6	10	1
17th	1953	435	9	-	2	6	30	4	6	1	8	10	-	2	25	11	8	6	8	8	3	7	14	18	9	6	11	2	4	1	2	14	2	43	12	2	23	6	4	30	2	6	2	9	22	2	1	10	7	6	10	1
18th	1963	435	8	1	3	4	38	4	6	1	12	10	2	2	24	11	7	5	7	8	2	8	12	19	8	5	10	2	3	1	2	15	2	41	11	2	24	6	4	27	2	6	2	9	23	2	1	10	7	5	10	1
19th	1973	435	7	1	4	4	43	5	6	1	15	10	2	2	24	11	6	5	7	8	2	8	12	19	8	5	10	2	3	1	2	15	2	39	11	1	23	6	4	25	2	6	2	8	24	2	1	10	7	4	9	1
20th	1983	435	7	1	5	4	45	6	6	1	19	10	2	2	22	10	6	5	7	8	2	8	11	18	8	5	9	2	3	2	2	14	3	34	11	1	21	6	5	23	2	6	1	9	27	3	1	10	8	4	9	1
21st	1993	435	7	1	6	4	52	6	6	1	23	11	2	2	20	10	5	4	6	7	2	8	10	16	8	5	9	1	3	2	2	13	3	31	12	1	19	6	5	21	2	6	1	9	30	3	1	11	9	3	9	1
22nd	2003	435	7	1	8	4	53	7	5	1	25	13	2	2	19	9	5	4	6	7	2	8	10	15	8	4	9	1	3	3	2	13	3	29	13	1	18	5	5	19	2	6	1	9	32	3	1	11	9	3	8	1
Census	Year	Size	AL	AK	AZ	AR	CA	CO	CT	DE	FL	GA	HI	ID	IL	IN	IA	KS	KY	LA	ME	MD	MA	MI	MN	MS	MO	MT	NE	NV	NH	NJ	NM	NY	NC	ND	OH	OK	OR	PA	RI	SC	SD	TN	TX	UT	VT	VA	WA	WV	WI	WY

[edit] Projected changes following the 2010 census

The U.S. Census Bureau will conduct a comprehensive census in April 2010 (2010 census). Based on the populations counted in each state, the United States Congress will be reapportioned based on the Equal Proportions Method defined above. The total number of voting representatives is expected to remain at 435, assuming no legislation passes that would modify the apportionment process. Since the Census Bureau releases population estimates every year, projections have been made that predict the states' populations as of April 2010. One study estimates that fourteen seats would shift between the states as follows:^[3]

Gain more than one	Gain one	Lose one		Lose more than one
Texas +4 Arizona +2 Florida +2	Georgia +1 Nevada +1 North Carolina +1 Oregon +1 South Carolina +1 Utah +1	California -1 Illinois -1 Iowa -1 Louisiana -1 Massachusetts -1	Michigan -1 Minnesota -1 Missouri -1 New Jersey -1 Pennsylvania -1	New York -2 Ohio -2

The 10-year national growth rate is 12.5%. In this estimate, the population of states losing seats grew at a slower rate and the population of states gaining seats grew at a faster pace. Louisiana is the only state losing a seat that is estimated to have lost population between 2000 and 2010, significantly due to the exodus precipitated by the damage caused by Hurricane Katrina. The losing states are in the industrial northeast and midwest, while gainers are in the southeast, southwest and Pacific northwest.^[3]

[edit] Notes

Delegate counts in italics represent temporary counts assigned by Congress until the next decennial census or by the U.S. Constitution in 1789 until the first U.S. Census.
Elections held in the year of a census use the apportionment determined by the previous census.