various alternative methods of treating the work activity of individuals entitled to disability insurance benefits under section 423 of this title or to monthly insurance benefits under section 402 of this title based on such individual’s disability (as defined in section 423(d) of this title), including such methods as a reduction in benefits based on earnings, designed to encourage the return to work of such individuals;

altering other limitations and conditions applicable to such individuals (including lengthening the trial work period (as defined in section 422(c) of this title), altering the 24-month waiting period for hospital insurance benefits under section 426 of this title, altering the manner in which the program under this subchapter is administered, earlier referral of such individuals for rehabilitation, and greater use of employers and others to develop, perform, and otherwise stimulate new forms of rehabilitation); and

any such benefit otherwise payable to the individual for such month (other than a benefit payable for any month prior to the 1st month beginning after the date on which the individual’s entitlement to such benefit is determined) shall be reduced by $1 for each $2 by which the individual’s earnings derived from services paid during such month exceeds an amount equal to the individual’s impairment-related work expenses for such month (as determined under paragraph (3)), except that such benefit may not be reduced below $0;

no benefit shall be payable under section 402 of this title on the basis of the wages and self-employment income of the individual for any month for which the benefit of such individual under section 423(a)(1) of this title is reduced to $0 pursuant to subparagraph (A);

entitlement to any benefit described in subparagraph (A) or (B) shall not terminate due to earnings derived from services except following the first month for which such benefit has been reduced to $0 pursuant to subparagraph (A) (and the trial work period (as defined in section 422(c) of this title) and extended period of eligibility shall not apply to any such individual for any such month); and

in any case in which such an individual is entitled to hospital insurance benefits under part A of subchapter XVIII by reason of section 426(b) of this title and such individual’s entitlement to a benefit described in subparagraph (A) or (B) or status as a qualified railroad retirement beneficiary is terminated pursuant to subparagraph (C), such individual shall be deemed to be entitled to such benefits or to occupy such status (notwithstanding the termination of such entitlement or status) for the period of consecutive months throughout all of which the physical or mental impairment, on which such entitlement or status was based, continues, and throughout all of which such individual would have been entitled to monthly insurance benefits under subchapter II or as a qualified railroad retirement beneficiary had such termination of entitlement or status not occurred, but not in excess of 93 such months.