Average quarterly household income in Mexico declined by 12.3 percent between 2008 and 2010, the National Institute of Statistics and Geography, or Inegi, said Friday.

Over the same two-year period, which was marked by the country's worst economic slump since the 1930s, average spending per quarter by Mexico's 29 million households fell by 3.8 percent.

Average quarterly Mexican household income last year at constant, or inflation-adjusted, prices came in at 34,936 pesos ($2,985) a quarter, or 11,645 pesos ($995) a month, Inegi said, down 12.3 percent from 39,823 pesos a quarter in 2008.

INEGI, meanwhile, said total quarterly Mexican household income, in inflation-adjusted terms, fell 6.8 percent from 2008 to last year.

Average household spending totaled 10,198 pesos ($871) a month in 2010.

More than 33 percent of those expenditures went toward food, beverages and tobacco, followed by 17.2 percent to cover the cost of transportation and communications services and 13.6 percent toward education and recreation.

The data also revealed the huge gap in spending patterns between affluent and low-income families, with the poorest 10 percent of households spending 49.9 percent on food, beverages and tobacco, compared with 22.9 percent for wealthy families.

By contrast, only 5.4 percent of the household spending of Mexico's poorest households went to education and recreation, far below the 19.5 percent allocated by the wealthiest households.

Mexico has a population of 112.7 million inhabitants, 51.2 percent of whom are women.

The largest segment of the population is the 12-29 age group, accounting for 31.9 percent of the total; followed by the 30-49 group, 26.3 percent; children 11 and under, 22.9 percent; and people over 50, 18.8 percent.

The average Mexican household was composed of 3.9 people in 2010, down from four people two years earlier, while the head of household had an average age of 48.3 last year, about the same as in 2008.