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Sample measurements read negative absorbance for the following reasons: The absorbance value of the reference is higher than the sample. The reference and the sample are interchanged. The sample is very dilute and close to the absorbance of the reference. In general, absorption represents the demand for a type of real estate contrasted with supply. When demand is less than supply, vacancy increases and absorption is negative. Negative absorption can indicate changes in the larger economy, such as a decline in employment due to the closing of a business.