Plain-language summary Driven systems — a chemical mixture kept reacting, a fluid continuously stirred, a living cell burning fuel — typically settle into one of several possible stable states or repeating patterns. A long-standing rule of thumb, the maximum entropy production (MEP) principle, guesses that such a system will choose whichever option dissipates energy fastest. The guess often works, but not always: sometimes the system settles instead on a lower-dissipation option. This paper asks what governs those failures. It splits the "cost" of a rare switch between states into two distinct parts: one tied to how much energy is dissipated (the quantity MEP cares about), and a separate, time-symmetric part that measures how much restless back-and-forth activity — called frenesy — the switch involves. When this second, activity-based part is what tips the balance, the system selects against the MEP guess. The central result is a clean inequality: the activity imbalance between the forward and backward switching routes can never exceed half of the dissipation circulating around the loop those two routes form. Equivalently, a single number η between −1 and +1 measures how strongly activity, rather than dissipation, is steering the choice; it reaches its extreme values exactly where the system hands off from one preferred route to another. The result also implies a strict no-go: at equilibrium, where nothing circulates, this activity imbalance is exactly zero. Sustained circulation — a genuinely non-equilibrium condition — is therefore required for activity-driven, anti-MEP selection to occur at all. The bound is not a new physical law but an exact identity of the standard least-cost-path (large-deviation) description of rare events. The accompanying code confirms it across random networks, chemical reaction networks, a rotating model system, and a spatial field model, and turns it into a practical diagnostic: from a single recorded trajectory — once the competing switching routes are identified — one can tell whether an observed choice was driven by activity, by dissipation, or by boundary effects. Why it matters Predicting which state a driven system will select is a basic, still-open problem across physics, chemistry, biology, and climate science, and several proposed selection principles — maximum entropy production, and related ideas such as dissipative adaptation — try to answer it by appealing to dissipation alone. This work shows that dissipation is only part of the story: a time-symmetric activity channel, invisible to those principles, can override them, and it does so specifically under non-equilibrium driving. Rather than refuting MEP, the result places it. MEP-like alignment holds only when the activity channel is quiet, and the inequality pins the size of the activity imbalance — the part that can reverse the outcome — to the circulating dissipation, with equality exactly at the hand-off between competing routes. The framework is also operational. Because its key quantities can be estimated from a single observed steady-state trajectory, the bound doubles as a diagnostic that classifies the mechanism behind an observed selection — activity-, dissipation-, or boundary-driven — once the relevant routes are known. That makes the ideas testable in simulation and, in principle, in experiments on active matter, chemical reaction networks, and other driven systems where competing stable states are the rule rather than the exception.
Shigeo Kaneko (Mon,) studied this question.