Governors from Mexico's 21 states and the federal district of Mexico City, mayors, judges, prosecutors and senior police and security officials were at the meeting hosted by President Felipe Calderon at the National Palace.

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Now the reform must to be approved by a majority of the 31 Mexican states and the Federal District (Mexico City).

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Today, Xochimilco is one of the 16 boroughs within the Mexican Federal District that makes up Mexico City proper.

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All this is harder still when cities expand beyond their political boundaries, creating problems of co-ordination (Mexico City is split between the Federal District and the surrounding State of Mexico, for example).

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Not including a handful of states where it has a hand in a coalition, it now controls only two of Mexico's 31 states, plus the Federal District, which makes up the centre of Mexico City.

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The Federal District contains less than half the population of greater Mexico city.

ECONOMIST: Mexico