goals For any year subsequent to the period described in subparagraph (B), the goal for establishment of the variable charge with respect to any covered product shall be to alter trade flows such that the average pollution intensity difference associated with such covered product is not greater than 10 percent. (3) Progression of variable charge (A) In general To the maximum extent practicable, the variable charges assigned to each tier of a covered product to achieve the goals described in paragraph (2) shall progress through each tier in a manner consistent with an increasing linear interpolation of the variable charge. (B) Exception With respect to any tier for a covered product and the variable charge assigned to such tier, the Board may recommend and the Secretary may finalize a variable charge that deviates from a linear interpolation of the variable charge as described in subparagraph (A), provided that such alteration allows for a higher likelihood that the goals described in paragraph (2) will be attained. (4) Minimization of domestic cost increases For purposes of this subsection, any variable charge shall be established in a manner which ensures that the goals described under paragraph (2) are attained while minimizing any potential increase in domestic costs. (d) Exceptions (1) Comparable to baseline pollution intensity In the case of any covered product for which the pollution intensity difference is not greater than 10 percent, the variable charge shall be zero. (2) Insufficient domestic production (A) In general In the case of any covered product for which the Secretary determines there is not sufficient domestic production with respect to such product, the variable charge shall be zero. (B) Definition (i) In general For purposes of this paragraph, the term sufficient domestic production means any covered product for which an equivalent product which is produced by domestic producers within the United States constitutes greater than the applicable percentage of domestic consumption of such