  At the heart of technology transitions lie complex processes of social and
industrial dynamics. The quantitative study of sustainability transitions
requires modelling work, which necessitates a theory of technology
substitution. Many, if not most, contemporary modelling approaches for future
technology pathways overlook most aspects of transitions theory, for instance
dimensions of heterogenous investor choices, dynamic rates of diffusion and the
profile of transitions. A significant body of literature however exists that
demonstrates how transitions follow S-shaped diffusion curves or Lotka-Volterra
systems of equations. This framework is used ex-post since timescales can only
be reliably obtained in cases where the transitions have already occurred,
precluding its use for studying cases of interest where nascent innovations in
protective niches await favourable conditions for their diffusion. In
principle, scaling parameters of transitions can, however, be derived from
knowledge of industrial dynamics, technology turnover rates and technology
characteristics. In this context, this paper presents a theory framework for
evaluating the parameterisation of S-shaped diffusion curves for use in
simulation models of technology transitions without the involvement of
historical data fitting, making use of standard demography theory applied to
technology at the unit level. The classic Lotka-Volterra competition system
emerges from first principles from demography theory, its timescales explained
in terms of technology lifetimes and industrial dynamics. The theory is placed
in the context of the multi-level perspective on technology transitions, where
innovation and the diffusion of new socio-technical regimes take a prominent
place, as well as discrete choice theory, the primary theoretical framework for
introducing agent diversity.
