What is the percentage of winning rate of improvement since Alain Vigneault became the coach of Vancouver Canucks in 2006 season?
winning rate refers to DIVIDE (w, SUM(w, l)); Vancouver Canucks is name of team where tmID = 'VAN'
Winning rate refers to DIVIDE(wins in year = '2005/2006'(ADD(wins+loses); improvement refers to SUBTRACT(DIVIDE(wins in year = '2005'(ADD(wins+loses), DIVIDE(wins in year = '2006'(ADD(wins+loses))

SELECT SUM(CASE WHEN T1.year = 2006 THEN CAST(T1.W AS REAL) * 100 / (T1.W + T1.L) ELSE 0 END) - ( SELECT CAST(W AS REAL) * 100 / (W + L) FROM Teams WHERE year = '2005' AND name = 'Vancouver Canucks' ) FROM Teams AS T1 INNER JOIN Coaches AS T2 ON T1.tmID = T2.tmID AND T1.year = T2.year INNER JOIN Master AS T3 ON T2.coachID = T3.coachID WHERE T1.name = 'Vancouver Canucks' AND T3.firstName = 'Alain' AND T3.lastName = 'Vigneault'