The reported prevalence of TS varies "according to the source, age, and sex of the sample; the ascertainment procedures; and diagnostic system", with a range reported between .4% and 3.8% for children ages 5 to 18. Robertson (2011) says that 1% of school-age children have Tourettes. According to Lombroso and Scahill (2008), the emerging consensus is that .1 to 1% of children have Tourettes, with several studies supporting a tighter range of .6 to .8%. Bloch and Leckman (2009) and Swain (2007) report a range of prevalence in children of .4 to .6%, Knight et al. (2012) estimate .77% in children, and Du et al. (2010) report that 1 to 3% of Western school-age children have Tourettes.

Question: In whose report was the percentage of school-age children with Tourettes estimated between .5% and .8%?
Answer: Bloch and Leckman

Question: Which report lists the second highest range estimate?
Answer: Robertson

Question: Which report lists the second smallest percentage?
Answer: Swain

Question: How many years is the age range where the range reported is between .4% and 3.8 in children%?
Answer: 13

Question: Which study occurred last, Swain or Bloch and Leckman?
Answer: Bloch and Leckman

Question: Which study reports a higher percentage of children have Tourettes, Bloch and Leckman or Knight et al.?
Answer: Knight et al.

Question: How many years after the Bloch and Leckman study was the Knight et al. study?
Answer: 3

Question: How many percentage points difference does Swain report is the range of prevalence of Tourettes in children.
Answer: .2

Question: Which report came out first, Du et al. or Knight et al.?
Answer: Du et al.

Question: How many years after Du et al.'s report came out was the Knight et al. report released?
Answer: 2