Having built up such momentum in its oil production as it entered the 1990s, the Company fully expected the trend to continue. Unfortunately, the Company's field-development strategy for the start of the 21st century – based on incremental infill drilling with horizontal wells and extensive waterflooding – had its momentum dissipated before the waterflooding projects, which require comprehensive reservoir studies, could be fully implemented. The natural production-rate decline of its major oil fields eventually caught up with the Company at the start of the millennium. In 1997, the 35-year old Yibal field began to decline in production. Two scientific papers published in 2003 showed a decline of about 12 percent annually since 1997, with 5 percent being the regional average.