In order to put into force and effect the policy of Congress by this chapter intended, the commission (1) upon request of the President, or (2) upon resolution of either or both Houses of Congress, or (3) upon its own motion, or (4) when in the judgment of the commission there is good and sufficient reason therefor, upon application of any interested party, shall investigate the differences in the costs of production of any domestic article and of any like or similar foreign article. In the course of the investigation the commission shall hold hearings and give reasonable public notice thereof, and shall afford reasonable opportunity for parties interested to be present, to produce evidence, and to be heard at such hearings. The commission shall report to the President the results of the investigation and its findings with respect to such differences in costs of production. If the commission finds it shown by the investigation that the duties expressly fixed by statute do not equalize the differences in the costs of production of the domestic article and the like or similar foreign article when produced in the principal competing country, the commission shall specify in its report such increases or decreases in rates of duty expressly fixed by statute (including any necessary change in classification) as it finds shown by the investigation to be necessary to equalize such differences. In no case shall the total increase or decrease of such rates of duty exceed 50 per centum of the rates expressly fixed by statute.
The President shall by proclamation approve the rates of duty and changes in classification specified in any report of the commission under this section, if in his judgment such rates of duty and changes are shown by such investigation of the commission to be necessary to equalize such differences in costs of production.
Any increased or decreased rate of duty or change in classification which has taken effect as above provided may be modified or terminated in the same manner and subject to the same conditions and limitations (including time of taking effect) as is provided in this section in the case of original increases, decreases, or changes.
Nothing in this section shall be construed to authorize a transfer of an article from the dutiable list to the free list or from the free list to the dutiable list, nor a change in form of duty. Whenever it is provided in any paragraph of Subtitle I of this chapter, or in any amendatory act, that the duty or duties shall not exceed a specified ad valorem rate upon the articles provided for in such paragraph, no rate determined under the provisions of this section upon such articles shall exceed the maximum ad valorem rate so specified.
The President is authorized to make all needful rules and regulations for carrying out his functions under the provisions of this section.
All uncompleted investigations instituted prior to June 17, 1930, under the provisions of sections 154 to 159  of this title, including investigations in which the President has not proclaimed changes in classification or increases or decreases in rates of duty, shall be dismissed without prejudice; but the information and evidence secured by the commission in any such investigation may be given due consideration in any investigation instituted under the provisions of this section.