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Nelson complexity index
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<p>The Nelson complexity index (NCI) is a measure to compare the secondary conversion capacity of a <a href="/facts/Petroleum_refinery/yeaW0UMv">petroleum refinery</a> with the primary distillation capacity. The index provides an easy metric for quantifying and ranking the complexity of various refineries and units. To calculate the index, it is necessary to use complexity factors, which compare the cost of upgrading units to the cost of crude distillation unit. </p>