A neo-institutional response matrix for explaining governance dynamics influencing infrastructure project cost misperformance

This paper operationalizes the Fifth Hand, an emergent theory of project behavior explaining cost misperformance in infrastructure projects, through a neo-institutional response matrix that captures institutional pressure and behavioral enactment across two governance regimes: (1) the pre-contract regime, where funding commitments are established at the decision-to-build; and (2) the post-contract regime, where delivery proceeds under contractual enforcement and audit oversight. Two indices—the Mode of Action Index and the Institutional Pressure Index—classify cost-relevant decision episodes and identify patterns of dominance, transition, entrenchment, and suppression across regimes. An illustrative case, the New Perth Bunbury Highway, shows how cost trajectories emerge from governance responses to divergence between approved funding and updated cost projections. Under heightened institutional pressure, adjustments are deferred, increasing the likelihood of discrete increases in funding. Under moderated pressure, revised projections are incorporated earlier through incremental adjustment. The response matrix explains how cost misperformance develops through successive governance decisions.