This cannot be correct if Y is defined to be factor income in terms of cash flow, that is to say, in terms of purchasing power placed into the hands of final consumers. If there are natural growth vectors causing parametric shift, the concept of equilibrium in a regime of laissez-faire becomes meaningless. It is only through credit expansion that long-term growth in the financial sense becomes possible. In principle, credit expansion can occur in either the consumers or firms sectors. The gap between instantaneously measured t1 and t2 represents accumulation to debt, not savings.
Investment is the process of improving the quantity or quality of capital.