The real exceptions to the above rules are caused by a prevention of the leveling influx and outflow of capital. Among nations in a low stage of civilization, there is wont to be a multitude of legal impediments in this respect. The existence of a difference of classes, of privileged corporations, etc., not only restrains the transition of workmen, but also of capital from one branch of industry to another. But even the mere routine of capitalists, that blind distrust of everything new so frequently characteristic of easily contented men, may produce the same result.[181-1] In the higher stages of civilization, patents for inventions and bank privileges, are causes of a lastingly higher rate of interest than is usual in the country.[181-2] Finally, since in many enterprises only a large amount of capital can be used at all, or at least with most advantage, the aggregation of which from many small sources is ordinarily much more difficult than the division of a large one into small fractional parts; the rate of interest for very small amounts of capital, and especially in the higher stages of civilization, is usually lower than that of large amounts of capital. We need only mention interest paid by savings-bank investments.[181-3] If circulating capital has been changed into fixed capital, its yield will depend upon the price of the particular goods in the production of which it has been made to serve. Compared with the cost of restoration of fixed capital, this yield may, in a favorable case, constitute an extraordinarily high rate of interest, in an unfavorable a very low one; and the former of these two extremes has a greater chance of being realized, in proportion as it is difficult to multiply fixed capital of the same kind; the latter, the more exclusively it can be employed in only one kind of production, and the longer time it takes to be used up by wear.[181-4] When fixed and circulating capital coöperate in production, the latter, because it can be more easily withdrawn, but also more easily replaced, first takes out its own profit, that is the profit usual in the country and leaves all the rest to the former. When fixed capital is sold, practically no attention is paid to what it originally cost. The purchaser pays only for the prospective revenue it will yield, which he capitalizes at the rate of interest usual in the country. The seller henceforth looks upon his gain as an accretion to capital, his loss as a diminution of capital, and no longer as high or low interest.[181-5] That accretion might be considered the wages, paid once for all, for the intelligent labor which governed the original investment of the capital, and _vice versa_.