Engel coefficient is the proportion of total food expenditure to total personal consumption expenditure. /kloc-According to the statistical data, Engel, a German statistician in the 20th century, drew a rule about the change of consumption structure: the less a family's income, the greater the proportion of family income (or total expenditure) spent on food, and with the increase of family income, the proportion of family income spent on food will decrease. By extension, the poorer a country is, the greater the average income (or average expenditure) of each national is spent on food, and this proportion shows a downward trend with the prosperity of the country. \x0d\x0d\ Engel's law formula: \x0d\ change percentage of food expenditure ÷ change percentage of total expenditure x 100%= ratio of food expenditure to total expenditure (r1) \ x0d \ or \ x0d \ change percentage of food expenditure x 67 income.