Oil pipelines for the purposes of capturing oil and transporting it illegally out of Nigeria for monetary gain. This process, known as "oil bunkering", is estimated to cost Nigeria as much as 400,000 barrels of crude oil per day. Typically, when the oil theft operation is finished, the pipeline is left open, which results in an oil spill. In addition to the spills caused by 'oil bunkering', oils spills can also occur as a result of the quality of the equipment being used to extract and transport the oil. These spills are referred to as 'operational spills' and can be caused by corrosion, a lack of regular maintenance of the equipment, and overall underinvestment in the equipment being used. 18.7% of the spills reported by Shell since 2011 are labeled to be 'operational spills'. Oil spills can also occur as a result of natural hazards causing damage to pipelines. In 1970, there was an oil spill from a Shell pipeline caused primarily by corrosion and operational failure resulting in over 250 barrels of oil spilled. The resulting effects included the pollution of the surrounding air, water, and soil, as well as, a loss of the surrounding ecological and aquatic species. Health problems in the surrounding areas were also cited as an impact of the oil spill. In 1978, another spill from a Shell pipeline due to corrosion and operational failure was reported to have leaked 580,000 barrels of oil. The resulting impacts were air, water, and soil pollution in the area of the spill. In 2006, a team of experts in environmental assessments from Nigeria, the United Kingdom, and the United States were independently organized to conduct a Natural Resource Damage Assessment in the Niger Delta. They concluded that over the past fifty years, around nine million to thirteen million barrels of oil had been estimated to have spilled in the Niger Delta. Shell is responsible for around fifty percent of the oil production in Niger Delta. Between 1998 and 2009, Shell oil was responsible for 491, 627 barrels of oil spilled, averaging about 41,000 barrels per year. In 2011, Shell started publishing the reports it has been required to take every time an oil spill occurs. These reports, titled 'Joint Investigation Visit' or JIV, record when the spill began, where the spill took place, the cause of the spill, and the estimated amount of oil lost. JIV reports are