Q: This task involves annotating the answer type to a given question that involve some kind of complex reasoning (including numerical reasoning). Note that the questions require looking at more than one part of the passage to answer. There are 3 possible answer types (i) spans, (ii) numbers and (iii) dates. If the answer can be found in the passage, label it as "span". If the answer is a number, label as "number". Similarly, label "date" if you think the answer to the given question is a date.
Passage: In 1906, at the suggestion of Governor Jose Celestino da Silva, the Portuguese government decided to replace the finta with a capitation . A decree of 13 September outlined new regulations. All heads of native households owed 500 reis annually unless they were under contract on agricultural plantations of more than 500 hectares or living in reinos producing at least 500,000 pounds of the valuable cash crops of coffee, cocoa or cotton. In those reinos where the capitation was collected, the liurai received half of all the revenues. The decree stipulated, furthermore, that all reinos with less than 600 heads of household were to be abolished, but this seems never to have been carried out. Liurais were forbidden to collect any tax or tribute but the capitation. With these measures, the Portuguese government sought to transform the reino into a fiscal unit and the liurai into a fiscal agent, while pushing independent cultivators into the more lucrative production of coffee . The head tax system was initially opposed by Manufahi and a few allies. In 1910, a commission was sent to take a census of the native population. It ascertained there were 98,920 heads of family eligible to pay tax in 73 or 75 loyal reinos. In disloyal reinos, such as Manufahi, which had seen fighting in 1907-08, the population had shrunk.
Question: How many years after the decree of 13 September was a commission sent to take a census of the native population?
A:
number