Last night I read the related chapter of Capital to find out why some authors apply term "tendency" between quotation marks. Is it something like the tendency of a clumsy man to trash his surroundings or like the tendency of Dwight Howard to dunk the ball? Obviously, in the same way as Jim Devine, "a Marxist economist", they use the quotation marks to imply a faint potential that somehow has no expression in the actual functioning of capitalist production: All right, Marx once propounded a highly speculative hypothesis but it was just a "tendency", but in reality, speaking of "inherent tendency" how about an inherent tendency for the relentless accumulation of capital? It is all nonsense. You don't have to be an economist to figure out that Marx merely indicates a GRADUAL progress with term "tendency", by which rate of profit gradually falls according to the growth of constant capital relatively to the variable capital.
Apparently, Marx didn't think it is necessary to explain the implication of the word "tendency" except than emphasizing the gradual process numerous times:
"This gradual change in the composition of capital... then the gradual growth of constant capital... lead to a gradual fall… ever-increasing quantity of means of production through a constantly decreasing quantity of labour… each particular lot of commodities in the total mass of products, absorbs less living labour… Alongside the development of productivity there develops a higher composition of capital, i.e., the relative decrease of the ratio of variable to constant capital… The increase in labour productivity consists precisely in that the share of living labour is reduced while that of past labour is increased, but in such a way that the total quantity of labour incorporated in that commodity declines; in such a way, therefore, that living labour decreases more than past labour increases… therefore the absolute mass of the profit produced by it, can, consequently, increase, and increase progressively, in spite of the PROGRASSIVELY drop in the rate of profit. etc. etc."
The law of the tendency of the rate of profit to fall, is not a negligible, non-inherent, phenomena of capitalist production. It is the "logical necessity" of the DEVELOPMENT of capitalist production. It is how the development of capitalist production (i.e. growth of constant capital relatively to variable capital, growth of productivity of labor) works. I suggest Jim Miller's article: