Initially, the program subsidized new construction, substantial rehabilitation, and tenant rents in existing housing. In 1978, the program was expanded to include a moderate rehabilitation component; and a voucher program for existing housing was added as a demonstration program in 1983 and made permanent in 1987. Unlike the original existing housing or certificate program, the voucher set no limits on unit rents. However, the subsidy was capped. Tenants with vouchers could rent units above otherwise-applicable market rent limits by paying the additional cost, without an increase in their subsidy. In 1998, Congress merged the certificate program into the voucher program. Tenants who receive Section 8 assistance will receive a voucher with a subsidy cap.