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Boise, Idaho • Republicans have controlled the Idaho Legislature for nearly six decades, but a national Associated Press analysis shows that the state GOP may have gained even more control last fall with the help of Republican-friendly districts.

The Associated Press used a new mathematical formula to scrutinize roughly 4,700 state House and Assembly seats up for election last year and found a decided advantage for Republicans in numerous states, including Idaho.

The analysis showed that Idaho is among the top 10 states in the country with the biggest "efficiency gap," or the percentage of seats won by Republicans beyond what would be expected based on their statewide average share of votes.

The formula compares the statewide average share of the vote that a party receives with the statewide percentage of seats the party won, taking into account that in politics, each percentage point share of statewide votes generally accounts for a 2 percentage point increase in seat share.

After the November election, 59 Republicans control the Idaho House, which has 11 Democrats. Democrats lost four seats to Republicans.

Under a redistricting plan approved in 2012, Idaho's House seats are divided among 35 districts — each district has two House seats and one Senate seat.

The AP did not include Senate seats in its analysis because not all of those positions were up for re-election nationwide in 2016. The data also doesn't identify any particular districts where the legislative map might give Republicans a boost.

In Idaho, districts for Congress and the state Legislature are drawn every 10 years by a six-member commission answerable only to the courts. The majority and minority party leaders in each legislative chamber each select one person to serve on the commission; the state chairmen of the Republican and Democratic parties also each select a commissioner.

At least two-thirds of the commissioners must vote to approve a map. Despite operating under the bipartisan system since 1992, plans can get caught up in lengthy legal battles before settling on new district boundaries.

The AP also calculated efficiency gap scores for the U.S. House elections, though experts caution those measurements are less statistically meaningful in states with few districts. Idaho has only two districts, both of which were won by Republicans in November. Idaho has a 13 percent efficiency gap heavily favoring Republican congressional candidates.

Nationally, the analysis found that Republicans may have won as many as 22 additional congressional seats over what would have been expected based on the average vote share in congressional districts across the country.