Family income and its percentage spent on food in the case of one hundred families gave the following bivariate frequency distribution. Calculate the coefficient of correlation and interpret its value.

Food Expenditure (in percent) Monthly Family Income (Rs.) 2000-3000 3000-4000 4000-5000 5000-6000 6000-7000 10-15 - - - 3 7 15-20 - 4 9 4 3 20-25 7 6 12 5 - 25-30 3 10 19 8 -