Q: This task is about reading the given passage and construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) its answer is a continuous text span from the paragraph. Avoid creating questions that (i) can be answered correctly without actually understanding the paragraph and (ii) uses same words or phrases given in the passage.
Modern Estonia is a fairly ethnically heterogeneous country, but this heterogeneity is not a feature of much of the country as the non-Estonian population is concentrated in two of Estonia's counties. Thirteen of Estonia's 15 counties are over 80% ethnic Estonian, the most homogeneous being Hiiumaa, where Estonians account for 98.4% of the population. In the counties of Harju (including the capital city, Tallinn) and Ida-Viru, however, ethnic Estonians make up 60% and 20% of the population, respectively. Russians make up 25.6% of the total population but account for 36% of the population in Harju county and 70% of the population in Ida-Viru county.
A:
What number of Estonia's counties are over 80% ethnic Estonian?