Rewrite each original sentence in order to make it easier to understand by non-native speakers of English. You can do so by replacing complex words with simpler synonyms (i.e. paraphrasing), deleting unimportant information (i.e. compression), and/or splitting a long complex sentence into several simpler ones. The final simplified sentences need to be grammatical, fluent, and retain the main ideas of their original counterparts without altering their meanings.
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Question: Zhengzhou is the province's capital and most populous city.

Answer: Zhengzhou is the province's capital. It has the highest population.

Question: However the registration law changed in 2006 and since March 2007 official vehicles have got standard number plates.

Answer: Official vehicles have not gotten standard plate numbers since 2006 because of the change of registration law in 2006.

Question: The aggregate income distribution is highly concentrated towards the top, with the top 6.37% earning roughly one third of all income, and those with upper-middle incomes control a large, though declining, share of the total earned income.

Answer:
The total income distribution is more to the top. The top 6.37% earns about one third of all income. People with upper-middle incomes control a large, though declining, share of the total earned income.