Shimshon Bichler and Jonathan Nitzan argue that most studies purporting to show empirical evidence of the labor theory of value often make methodological errors by comparing the total labor value to total price of multiple economic sectors, which results in a strong overall correlation but this is a statistical exaggeration; the authors argue that the correlations between labor value and price in each sector are often very small if not insignificant. Bichler and Nitzan also argue that because it is difficult to quantify a way to measure abstract labor, researchers are forced to make assumptions. However, Bichler and Nitzan argue these assumptions involve circular reasoning: