The accumulated capital can be :

- Technical: physical capital (fixed capital) constituted in particular by the stock of durable goods mobilised during the production process (e.g. machines).

- Public: it represents all investments made by public administrations (A.Pu).

- Technological: it represents all the technological advances held by a company and incorporated into its products. It is the stock of knowledge and technology related to production. It can be illustrated by process innovations (e.g. the conveyor belt of Fordism).

- Human: it can represent a stock of knowledge or skills valued in the labour factor. It is also the level of qualification, skills and health of the workforce which is a guarantee of labour productivity and becomes a source of investment for companies (G. Becker). Human capital can be the source of investments financed individually (e.g. spending by families on schooling) or collectively (e.g. the state financing education).

This capital constitutes a transmissible and accumulable stock (which is always increasing). They can benefit the greatest number of people because of positive externalities. Technical progress is then considered as a public good which is an explanatory entry to the continuity of growth in the long term and the continuous diffusion of PT which stimulates productivity gains.

Returns are then increasing, which calls into question the pessimistic visions of stationary growth in the long term set out, in particular by A. Smith, D. Ricardo and, to a certain extent, in the early work of J. A. Schumpeter.

Continuity of growth then seems possible.

Technical progress, in this perspective of endogenous growth, is no longer discontinuous and exogenous (Solow's heavenly manna or an unexplained residue of Solow, Carré, Dubois and Malinvaud). It is incorporated into the factors of production and promotes ever-increasing productivity gains. Solow's diminishing returns are exceeded and the Cobb-Douglas production function Y = f (K; L) becomes richer and becomes: Y = f (A; K; L).

Technical progress, which is thus diffused to all economic activities, takes on the dimension of a public good, non-rival and non-exclusive.

For example, technological innovations (according to Schumpeter's typology of the five main innovations) stimulate the qualification of the labour force by encouraging the learning of new production methods that improve TFP.
Moreover, the use of computers in a computer-aided production (CAP) logic promotes not only the learning of computers within the company but also outside the workplace, in other activities. The "learning by doing" or learning effects within the company favour the increase in labour productivity but also the increase in the level of technique incorporated by each individual in a society. This accumulation further promotes the continuity of progress and hence growth.
The role of innovations is fundamental in the new models of endogenous growth because they spread horizontally throughout the production process through the intermediate goods and services that are incorporated during the stages of production. A strong division of labour accentuates the effect (Young's model of 1928).
Innovations also play a role in a more vertical perspective with the notion of product quality.

Organisational innovations (Fordism, Toyotism, etc.) produced by one branch of activity are also generalised to all other activities and sectors, thus stimulating productivity gains and also pushing back the limits of the law of diminishing returns.

The growing stock of knowledge, which is a public good (R. Barro, 1990), encourages the raising of skill levels and the use of new technologies.