WITH
 InsuranceWithCounts AS (
 SELECT
 tiv_2016,
 COUNT(*) OVER(PARTITION by tiv_2015) AS tiv_2015_count,
 COUNT(*) OVER(PARTITION by lat, lon) AS city_count
 FROM Insurance
 )
SELECT ROUND(SUM(tiv_2016), 2) AS tiv_2016
FROM InsuranceWithCounts
WHERE tiv_2015_count > 1
 AND city_count = 1;