The majority of Mongolians and Kazakh were originally traveling nomads. Since they are herding animals they must constantly move around to find green pasture for there animals. So that explains why Kazakh people in Western Mongolia.
Do know when Mongolia and Kazakstan became more democratic that thousands of Kazakh people from Western Mongolia left for Kazakhstan thinking things were economically better there. Turns out they were wrong so many returned back to Mongolia.
Kazakhstan is also close to Mongolia.
See map:
http://farm3.static.flickr.com/2403/252071..._1454f4fac9.jpgBetter Map. You can see how close Kazakhstan is to Mongolia. Less than 30 miles separate them.
http://www.reisenett.no/map_collection/com.../Kazakhstan.jpgIn 2002 this was the breakup for Kazakhstan:
QUOTE
Kazakh 55.8%, Russian 28.3%, Ukrainian 3.3%, Uzbek 2.6%, German 1.8%, Uyghur 1.5%, other 5.0%
There population was 15.6 million in 2008. They lost 800000 people. Mostly Russian and Ukrainians that left after Soviet Union started breaking up in 1989.
This breakup for Mongolia in 2000:
QUOTE
Mongol (predominantly Khalkha) 94.9%, Turkic (of which Kazak is the largest group) 5%, other (including Chinese and Russian) 0.1%
This population was 2,996,081 in 2008.