delivered the opinion of the court:
This is an original action under article IV section 3 of the Illinois Constitution of 1970 (Ill. Const. 1970, art. IV § 3) challenging the validity of the redistricting plan approved by the Illinois Legislative Redistricting Commission and filed with the Secretary of State following the federal decennial census conducted in the year 2000. Plaintiffs are three registered Illinois voters, Diedra L. Cole-Randazzo of Rochester, Harry R. Walton of Decatur, and Kamela S. Wood of Springfield. Defendants are the Attorney General of Illinois, the Illinois Secretary of State, the members of the Illinois State Board of Elections, and the Illinois Legislative Redistricting Commission (the Commission) and its members.
Plaintiffs initiated this proceeding by filing a motion for leave to file a complaint in accordance with Supreme Court Rule 382 (155 Ill. 2d R. 382). Plaintiffs’ motion was granted and a briefing schedule was established. The matter was subsequently set for oral argument. Plaintiffs were allowed to file an amended complaint. The court also permitted additional parties to intervene. James “Pate” Philip, President of the Illinois Senate, and Lee Daniels, Minority Leader in the Illinois House, were allowed to intervene as additional plaintiffs. Emil Jones, Jr., the Minority Leader of the Illinois Senate, and John Tally, a registered voter, were allowed to intervene as additional defendants.
In their complaint, as amended, plaintiffs challenge the boundaries established by the Commission for the 51st Legislative (Senate) District, which encompasses the 101st and 102nd Representative Districts. They also challenge the boundaries fixed by the Commission for the 99th and 100th Representative (House) Districts. Interveners Philip and Daniels attack the Commission’s redistricting plan as a whole, as well as various specific legislative and representative districts, including Legislative Districts 29, 38, 51 and 55 and Representative Districts 15, 18, 35, 36, 75, 113 and 114.
Legislative redistricting maps approved and filed under section 3 of article IV of the Illinois Constitution of 1970 (Ill. Const. 1970, art. IV § 3) must meet four requirements. First, the districts formed must be substantially equal in population. Second, the districts must be configured in such a way as to provide adequate representation to minorities and other special interests protected by state and federal law. Third, the districts must be compact and contiguous. Fourth, the maps must meet all legal requirements regarding political fairness. People ex rel. Burris v. Ryan, 147 Ill. 2d 270, 296 (1992).
The challengers to the redistricting plan at issue in this case make no claim that the districts fail to meet the requirement of equality of population or that the configuration of those districts denies adequate representation to any minorities and other special interests protected by state and federal law. The contiguity of the districts is unquestioned. The legal requirements regarding political fairness are not alleged to have been infringed. The only dispute concerns whether the various districts identified by the original and intervening plaintiffs meet our state’s “compactness” requirement.
The arguments presented by the original and intervening plaintiffs are essentially the same. They contend that by reconfiguring various districts, the map could be improved to make certain legislative and representative districts more compact than they are under the plan adopted by the Commission and filed with the Secretary of State. The intervening plaintiffs have attempted to quantify the potential enhancement in compactness using mathematical tests based on geographical measurements and district shapes. The original plaintiffs rely solely on visual observation.
Based on visual observation, the compactness of the districts formed under the plan before us today is not discernibly different from the compactness of the districts established under the plan approved by this court 10 years ago in People ex rel. Burris v. Ryan, 147 Ill. 2d 270, 296 (1992). While some of the new districts are certainly more elongated than others, the same was true of districts drawn under the old map. Overall, the level of compactness has changed little.
The data submitted by the intervening plaintiffs confirm this observation. The various representative and legislative districts were analyzed by the intervening plaintiffs’ experts using two different tests. The first, known as the dispersion test, compared a district’s area to the area of the smallest circle that circumscribed that area. The second, called the perimeter test, measured irregularities in the boundaries of districts. The highest score a district could receive was one. The lowest was zero. The mean dispersion score for representative districts under the old map and the mean dispersion score for representative districts under the map challenged here differed by only one one-hundreth of a point (0.01). That was also the case with the mean dispersion score for legislative districts.
The results yielded by the perimeter test were comparable. Under that test, the difference in mean scores for representative districts under the new map and representative districts under the previous map was three one-hundredths of a point (0.03). For the old and new legislative districts, the difference in mean scores was four one-hundredths of a point (0.04).
The original and intervening plaintiffs suggest alternatives to the present map which would yield some increases in compactness both visually and under the dispersion and perimeter tests. The fact that more compact formulations can be devised is not, however, a sufficient basis for invalidating a map duly approved and filed according to law. That is so for two reasons. First, as indicated earlier in this opinion, compactness is only one of several factors that must be taken into consideration in setting the boundaries for legislative and representative districts. No matter how compact proposed districts may be geographically, those districts will not suffice under the law unless they comply with each of the additional factors we have enumerated.
The need to take the additional factors into account was specifically acknowledged in the affidavit of Professor Richard Niemi, one of the intervening plaintiffs’ experts. Significantly, however, neither the original nor the intervening plaintiffs have addressed the implications of their proposed alternatives with respect to those factors. The materials they have submitted are silent on the question of how the proposed alternatives would compare in terms of equality of population, the provision of adequate representation to any minorities and other special interests protected by state and federal law, or adherence to the legal requirements regarding political fairness. Accordingly, we have no basis for assessing whether the proposed alternatives would be legally acceptable and, if so, whether they would be superior, on balance, to the plan approved and filed by the Commission.
Second, a redistricting plan approved and filed by the Commission is presumed to be valid. Ill. Const. 1970, art. IV § 3(b). Schrage v. State Board of Elections, 88 Ill. 2d 87, 92 (1981). Even if a proposed alternative map would meet the other legal requirements, in addition to the requirement of compactness, parties opposing a redistricting plan approved and filed by the Commission must establish not only that their map is superior, but that the map approved by the Commission is against the manifest weight of the evidence. People ex rel. Burris, 147 Ill. 2d at 296. The original and intervening plaintiffs have made no such showing. Indeed, the question of how well or poorly the redistricting map approved and filed by the Commission advances requirements beyond compactness is an issue the challengers do not even address.
For the foregoing reasons, the requests by the original and intervening plaintiffs for a declaratory judgment invalidating the redistricting plan approved and filed by the Commission and for an order requiring reconfiguration of districts formulated under that plan are hereby denied. Judgment is entered for defendants. The mandate of this court shall issue immediately.
So ordered.