A ballot initiative is a means by which a petition signed by a certain minimum number of registered voters can bring about a public vote on a proposed statute or constitutional amendment. Ballot initiatives are also called, depending on the state, "popular initiatives," "voter initiatives," "citizen initiatives" or just "initiatives."

Twenty-four states allow ballot initiatives. Each state has its own requirements for how many signatures are required, how many days can be spent collecting the signatures and when petitions must be turned in. States also vary on the average amount of money spent by initiative committees to support or oppose ballot measures.

Alaska

Number of signatures: 25,857
Deadline: January 17, 2012
Average spent per initiative (2010): $375,722.60

Arizona

Number of signatures: 172,808
Deadline: July 5, 2012
Average spent per initiative (2010): $773,718.46

Arkansas

Number of signatures: 62,507
Deadline: July 6, 2012
Average spent per initiative (2008): $303,874.60

California

Number of signatures: 504,742
Deadline: April 20, 2012
Average spent per initiative (2010): $16,831,850.50

Colorado

Number of signatures: 85,853
Deadline: August 6, 2012
Average spent per initiative (2010): $1,155,429.89

Florida

Number of signatures: 676,811
Deadline: February 1, 2012
Average spent per initiative (2010): $3,871,520.14

Idaho

Number of signatures: 47,432
Deadline: April 30, 2012
Average spent per initiative (2010): $0

Maine

Number of signatures: 57,277
Deadline: January 30, 2012
Average spent per initiative (2010): $912,457.88

Massachusetts

Number of signatures: 68,911
Deadline: August 1, 2012
Average spent per initiative (2010): $2,262,846.67

Michigan

Number of signatures: 258,087
Deadline: July 9, 2012
Average spent per initiative (2010): $150

Missouri

Number of signatures: 91,818
Deadline: May 6, 2012
Average spent per initiative (2010): $0

Montana

Number of signatures: 24,337
Deadline: June 22, 2012
Average spent per initiative (2010): $258,116

Nebraska

Number of signatures: 7% of registered voters in signatures at the filing deadline.
Deadline: July 6, 2012
Average spent per initiative (2010): $52,536.70

Nevada

Number of signatures: 72,352
Deadline: November 9, 2010
Average spent per initiative (2010): $96,825

North Dakota

Number of signatures: 13,452
Deadline: August 8, 2012
Average spent per initiative (2010): $187,972

Ohio

Number of signatures: 115,574
Deadline: July 4, 2012
Average spent per initiative (2010): $0

Oklahoma

Number of signatures: 82,781
Deadline: September 7, 2012
Average spent per initiative (2010): $478,907.27

Oregon

Number of signatures: 87,213
Deadline: July 6, 2012
Average spent per initiative (2010):

South Dakota

Number of signatures: 15,854
Deadline: November 1, 2011
Average spent per initiative (2010): $1,729,594.27

Utah

Number of signatures: 97,119
Deadline: April 15, 2012
Average spent per initiative (2010): $41,542.75

Washington

Number of signatures: 240,229
Deadline: July 6, 2011
Average spent per initiative (2010): $6,991,928.56

Wyoming

Number of signatures: 28,623
Deadline: February 13, 2012
Average spent per initiative (2010): $0