Results of these studies have also proved inconsistent and in some cases contradictory. For example, Cho studied the relationship between the number of people living below the poverty line in major cities and the commission of the FBI's seven index crimes. He found no relationship, meaning that those cities that had a higher percentage of their population living below the poverty line could not be correlated with higher crime rates. On the other hand, Ehrlich found a positive correlation when he used a different method of operationalizing poverty. Ehrlich found that as the percentage of households receiving less than half of the median family income increased or decreased in 1940, 1950, and 1960 the number of property crimes similarly responded. Since these were periods of overall decrease in the percentage of families falling below the 1/2 median income figure he found that property crimes decreased proportionally. Structural poverty and homicide [particularly acquaintance homicides] were found to be correlated by Loftin and Hill, Messner, and Smith and Parker. It appears that in bad economic times acquaintance homicides go up, possibly as a result of being unable to cope with such stressful situations and then lashing out as those closest around them