Database: world_development_indicators
Question: Please calculate the average of Arms imports (SIPRI trend indicator values) of the European & Central Asian countries.
SQL: SELECT CAST(SUM(T2.Value) AS REAL) / COUNT(T1.CountryCode) FROM Country AS T1 INNER JOIN Indicators AS T2 ON T1.CountryCode = T2.CountryCode WHERE T1.Region = 'Europe & Central Asia' AND T2.IndicatorName = 'Arms imports (SIPRI trend indicator values)'