Breaking from two decades of tradition, this year's election exit poll is set to include surveys of voters in 31 states, not all 50 as it has for the past five presidential elections, according to multiple people involved in the planning. The decision by the National Election Pool - a joint venture of the major television networks and The Associated Press - is sure to cause some pain to election watchers across the country. Voters in the excluded states will still be interviewed as part of a national exit poll, but state-level estimates of the partisan, age or racial makeups of electorates won't be available as they have been since 1992. The lack of data may hamper election night analyses in some states, and it will almost certainly limit post-election research for years to come. Here is a list of the states that will be excluded from coverage: Alaska, Arkansas, Delaware, District of Columbia, Georgia, Hawaii, Idaho, Kentucky, Louisiana, Nebraska, North Dakota, Oklahoma, Rhode Island, South Carolina, South Dakota, Tennessee, Texas, Utah, West Virginia and Wyoming.