Do girls in undeveloped countries have menarche later?

Variable: It depends on the body weight which is dependent on nutrition. So it is related to socioeconomic factors of the individual person. In general in under developed world due to poor nutrition on an average menarche is later than in developed world.

Some do: Inadequate nutrition sometimes delays menarche, however the closer to the equator a young girl is, the more likely she will start her period earlier. The more northern latitudes tend to delay a menarche. In the USA over the past 50 years the average age of menarche is lowering from age 12 to 11 due to better nutrition and earlier growth spurts.