Sadly I cannot measure the impact on the jury vote in 2008 and 2009 ....
There are no split vote results available on the Internet.
In 2008 the juries were only back-up in both the semis and the final.
In 2009 the juries were back-up in semis (+ joker) and 50% in the final.
From 2010 onward the juries have 50% in both the semis and the final.