Second, according to the Bortkiewiczian interpretation of Marx's value theory, values and prices constitute two distinct and independent "systems". With respect to relative magnitudes, prices do not depend on values, and values do not depend on prices. Prices of outputs depend on the prices of the inputs used to produce them, while values of outputs depend on the values of the inputs used to produce them. In contrast, the TSSI is a "single-system" interpretation since it holds that, in Marx's theory, (a) prices of outputs depend in the aggregate on the so-called "value rate of profit" (the ratio of surplus-value to capital invested), while (b) businesses' investments of capital value, and thus the values of the outputs produced, depend partly on the prices of the inputs acquired by means of these investments. Value and price are therefore determined interdependently, though they remain distinct.