Cite as: 588 U. S. ____ (2019) 27 KAGAN, J., dissenting Nor is there any reason to doubt, as the majority does, the competence of courts to determine whether a district map “substantially” dilutes the votes of a rival party’s supporters from the everything-but-partisanship baseline described above. (Most of the majority’s difficulties here really come from its idea that ideal visions set the baseline. But that is double-counting—and, as already shown, wrong to boot.) As this Court recently noted, “the law is full of instances” where a judge’s decision rests on “estimating rightly . . . some matter of degree”—including the “substantial[ity]” of risk or harm. Johnson v. United States, 576 U. S. ___, ___ (2015) (slip op., at 12) (internal quotation marks omitted); see, e.g., Ohio v. American Express Co., 585 U. S. ___, ___ (2018) (slip op., at 9) (determining “substantial anticompetitive effect[s]” when applying the Sherman Act); United States v. Davis, ante, at 7–10 (KAVANAUGH, J., dissenting) (cataloging countless statutes requiring a “substantial” risk of harm). The majority is wrong to think that these laws typically (let alone uniformly) further “confine[ ] and guide[ ]” judicial decisionmaking. Ante, at 28. They do not, either in themselves or through “statutory context.” Ibid. To the extent additional guidance has developed over the years (as under the Sherman Act), courts themselves have been its author—as they could be in this context too. And contrary to the majority’s suggestion, see ibid., courts all the time make judgments about the substantiality of harm without reducing them to particular percentages. If courts are no longer competent to do so, they will have to relinquish, well, substantial portions of their docket. And the combined inquiry used in these cases set the bar high, so that courts could intervene in the worst partisan gerrymanders, but no others. Or to say the same thing, so that courts could intervene in the kind of extreme gerrymanders that nearly every Justice for decades has thought to violate the Constitution. See supra, at 13.