Definition: In this task, you're expected to write answers to questions involving multiple references to the same entity. The answer to the question should be unambiguous and a phrase in the paragraph. Most questions can have only one correct answer.
Input: Passage: As of 2013, Ratanakiri Province had a population of approximately 184,000. Its population nearly doubled between 1998 and 2013, largely due to internal migration. In 2013, Ratanakiri made up 1.3% of Cambodia's total population; its population density of 17.0 residents per square kilometer was just over one fifth the national average. About 70% of the province's population lives in the highlands; of the other 30%, approximately half live in more urbanized towns, and half live along rivers and in the lowlands, where they practice wetland rice cultivation and engage in market activities. Banlung, the provincial capital located in the central highlands, is by far the province's largest town, with a population of approximately 25,000. Other significant towns include Veun Sai in the north and Lomphat in the south, with populations of 2,000 and 3,000 respectively.In 2013, 37% of Ratanakiri residents were under age 15, 52% were age 15 to 49, 7% were age 50 to 64, and 3% were aged 65 or older; 49.7% of residents were male, and 50.3% were female. Each household had an average of 4.9 members, and most households (85.6%) were headed by men.While highland peoples have inhabited Ratanakiri for well over a millennium, lowland peoples have migrated to the province in the last 200 years. As of 2013, various highland groups collectively called Khmer Loeu made up approximately half of Ratanakiri's population, ethnic Khmers made up 36%, and ethnic Lao made up 10%. Within the Khmer Loeu population, 35% were Tampuan as of 1998, 24% were Jarai, 23% were Kreung, 11% were Brou, 3% were Kachok, and 3% were Kavet, with other groups making up the remaining one percent. There are also very small Vietnamese, Cham, and Chinese minorities.  Though the official language of Ratanakiri (like all of Cambodia) is Khmer, each indigenous group speaks its own language. Less than 10% of Ratanakiri's indigenous population can speak Khmer fluently. 
Question: What is the largest demographic bracket in Ratanakiri Province?

15 to 49.