WHO recommends breastfeeding for 2 years, but rates do vary considerably by country.

The highest rates are in sub-saharan Africa, and they demonstrate the importance that breastfeeding has in fertility control as well as infant and maternal health, since contraceptive use is generally low in this region. Rates of breastfeeding are also high in Scandinavian countries, and one might hypothesize that state funded health care, long paid maternity leaves, and societal acceptance of public breastfeeding are among the impacting factors.

In contrast, the lowest rates of breastfeeding are seen in France, the UK, and the US. Not only are breastfeeding rates at birth lower in these countries, but the rate of breastfeeding in the US drops to 20% at 6 months.

http://www.lalecheleague.org/cbi/bfstats03.html