Q-86. A risk manager gathers five years of historical returns to calculate the Kendall τ correlation coefficient for stocks X and Y. The stock returns for X and Y from 2010 to 2014 are as follows:

Year	X	Y
2010	5.0%	-10.0%
2011	50.0%	-5.0%
2012	-10.0%	20.0%
2013	-20.0%	40.0%
2014	30.0%	15.0%

What is the Kendall τ correlation coefficient for the stock returns of X and Y?