Sec. 14. #Tariff changes and business uncertainty.# Another variable influence in American business has been the tariff.  Every tariff revision, whether the rates go upward or downward, shifts somewhat the relative opportunities and profitableness of different industries.  Some of these call for far-reaching readjustments of investments and of productive forces.  Some persons gain and some lose by every such change.  It is observed that a reduction of tariff rates seems to have a more disturbing effect upon business than does an increase.  This probably is because the industries favored by protective tariffs in America are those most fully within the circle affected by crises; whereas most of the consumers adversely affected by a rise of tariff rates are outside the commercial circles where short-time credit is common and where the rapid readjustment of investment leads to a financial crisis.  It never has been convincingly shown, however, that there is any large measure of correspondence in time (not to say causal relation) between tariff revisions and crises.[13]

Sec. 15. #Rhythmic changes in weather and in crops#.  A psychological movement, once started, accumulates force and momentum up to a certain point where a reaction begins.  This rhythmic movement as it appears in the capitalization of enterprises is favored and magnified, we have seen, by the wide use of credit and by the constantly changing technical and physical conditions of industry.  These call for constant revaluations of the sources of incomes, thus destroying customary and habitual valuations.  But why should the cycle begin or end at one point of time rather than at another; and what determines the length of the cycle?  Some of the new dynamic forces such as inventions and growth of population are distributed pretty regularly along the line, so that their influences are nearly equalized.  But occasionally some large impulse may serve to start a swing and if this impulse is somewhat regularly repeated, it may serve to keep up the rhythmic motion.  True, the lack of coincidence in the impact of various influences which occur accidentally, such as political changes, wars, and the rapid opening of new routes of transportation, would serve to hasten or to retard, perhaps for a time quite to alter, what would otherwise be the rhythm of the cycle.  That there is nevertheless, a noticeable degree of regularity in the recurrence of crises may be due to the presence of one dominating factor.

Alternation of good and poor harvests has always seemed to be favorable to business prosperity.  In America since about 1865, farm products have constituted the larger part of our exports, so that a succession of large harvests has usually acted to stimulate exports (one of the features of a period of prosperity), to give us a larger credit balance in international trade, and to reduce the rate of exchange.  Large harvests of the staple agricultural crops in America have been