Deadweight loss from a tax is proportional to the square of the tax rate: \(\text{DWL} \propto t^2\). If the tax doubles (\(t \to 2t\)), then \(\text{DWL} \propto (2t)^2 = 4t^2\). So the deadweight loss increases by a factor of four. This is why large taxes are disproportionately inefficient.