In favor of the specific duty is the ease of collection, since the article has only to be weighed or measured and then assessed. But it is often inadequate, since one yard of cloth or one pound of dye may be many times more valuable than another, and so with many other articles. One practical objection to the _ad valorem_ method is the opportunity which is afforded for fraud in the matter of valuation, since in many cases it is difficult to ascertain the real value of the article taxed. _The Protective Tariff._--From the beginning of our existence as a nation, reliance upon customs duties as a chief source of revenue has been a part of our established policy. In 1921 the receipts from this source were $308,025,102; and in many earlier years they were nearly half of the entire ordinary income of the national government. Great diversity of opinion, however, has existed in regard to what articles should be taxed and the amount that should be imposed. The Republican party has always insisted upon a tariff not only for revenue but also for protection to American industries and American labor against the cheap labor of the Old World. The Democratic party, on the other hand, has generally opposed the protective feature and insisted upon a tariff primarily for revenue.[35] [35] But in 1916 a Democratic Congress laid a protective tariff on imported dyestuffs to encourage a home industry. _The Preparation of a Tariff Bill_ devolves upon the ways and means committee of the house of representatives, where all revenue bills must originate.[36] In 1916 Congress provided for the creation of a bi-partisan Tariff Commission to investigate the operation of tariff laws and to make reports with a view to furnishing Congress with information for its guidance in the preparation of tariff bills. [36] The senate, however, has the right to propose amendments. Thus the tariff bill of 1894 was amended by the senate in nearly a thousand particulars. Again, the tariff bill of 1909 was so altered by the senate that it was in many respects a new bill, and the differences between the two houses were settled by a conference committee. _The Maximum and Minimum Principle._--In 1909 Congress adopted for the first time the maximum and minimum principle of fixing tariff rates. The law provided for a maximum and a minimum rate on many articles and authorized the President to apply the minimum rate to goods imported from countries which extend the same concession to articles imported by their citizens from the United States and to apply the maximum rate to others. _Reciprocity Treaties._--At various times in the past reciprocity treaties have been negotiated with foreign countries by which it was provided that lower rates should be levied on articles imported from such countries in return for reciprocal concessions of a similar kind from them; or that there should be free admission of articles by one country from the other.