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: Between 2000 and 2009, school enrollment declined by 121,000 students, and the number of teachers increased by 15,000. The student:teacher ratio was the eighth lowest in the country, 13:1. At $16,000, its per student spending was the nation's highest.
Question: How many years did it take for school enrollment to decline by 121,000 students?
number