Statistics are very hard to find on the Family Provisions Act.  Unlike criminal law I haven’t found any source of information other than the cases published on “Australasian Legal Information Institute” web site.  So the information you find on this page has been compiled from raw data by me.  If you have any corrections of better sources I would love to hear them. These statistics only show cases that went to the Supreme Court.
Other research suggests that 75% of cases are settled out of court and therefor the number of people involved in disputes would be much higher than shown here. FYI the chances of being murdered in NSW is about 2 in every 100,000 people.  That's the same as being sucked into a family provisions dispute.

Estimate cost of disputes (inc out of court settlements) just in NSW
2011                   $40 million
2010                   $32 million

 2010 2009 2008 2007 Case per 100K
 NSW5644  1.17
 VIC7624 0.21
 SA44 11 0.46
 QLD9646 0.26
 TAS2100 0.37
 WA 2300 0.17

The growth in will contests
I have compiled figures using data from cases published through the Australasian Legal Information Institute website database of NSWSC cases14.  The figures below show the growth in FPA claims over the 11 years 1998 - 2009.  As the majority of claims are by adult children the changes show an increase not explained by changes to the Act but an increased willingness to contest a will.  With the introduction of the notional estate rules this increase will accelerate in 2012 and beyond.

Data from NSWSC Annual Review 1998-2009 (no data given in 2003/4)
1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009
464          465         440         481         505         --         --         578         696         594         781         605

NSW case stats 2014

NSW case stats 2013

NSW case stats 2012

NSW case stats 2011