prior to its adoption of sfas no .
123 ( r ) , the company recorded compensation expense for restricted stock awards on a straight-line basis over their vesting period .
if an employee forfeited the award prior to vesting , the company reversed out the previously expensed amounts in the period of forfeiture .
as required upon adoption of sfas no .
123 ( r ) , the company must base its accruals of compensation expense on the estimated number of awards for which the requisite service period is expected to be rendered .
actual forfeitures are no longer recorded in the period of forfeiture .
in 2005 , the company recorded a pre-tax credit of $ 2.8 million in cumulative effect of accounting change , that represents the amount by which compensation expense would have been reduced in periods prior to adoption of sfas no .
123 ( r ) for restricted stock awards outstanding on july 1 , 2005 that are anticipated to be forfeited .
a summary of non-vested restricted stock award and restricted stock unit activity is presented below : shares ( in thousands ) weighted- average date fair .

Shares (in thousands)
Weighted- Average Grant Date Fair Value
Non-vested at December 31, 2006:
2,878
$13.01
Issued
830
$22.85
Released (vested)
(514)
$15.93
Canceled
(1,197)
$13.75
Non-vested at December 31, 2007:
1,997
$15.91

as of december 31 , 2007 , there was $ 15.3 million of total unrecognized compensation cost related to non-vested awards .
this cost is expected to be recognized over a weighted-average period of 1.6 years .
the total fair value of restricted shares and restricted stock units vested was $ 11.0 million , $ 7.5 million and $ 4.1 million for the years ended december 31 , 2007 , 2006 and 2005 , respectively .
employee stock purchase plan the shareholders of the company previously approved the 2002 employee stock purchase plan ( 201c2002 purchase plan 201d ) , and reserved 5000000 shares of common stock for sale to employees at a price no less than 85% ( 85 % ) of the lower of the fair market value of the common stock at the beginning of the one-year offering period or the end of each of the six-month purchase periods .
under sfas no .
123 ( r ) , the 2002 purchase plan was considered compensatory .
effective august 1 , 2005 , the company changed the terms of its purchase plan to reduce the discount to 5% ( 5 % ) and discontinued the look-back provision .
as a result , the purchase plan was not compensatory beginning august 1 , 2005 .
for the year ended december 31 , 2005 , the company recorded $ 0.4 million in compensation expense for its employee stock purchase plan for the period in which the 2002 plan was considered compensatory until the terms were changed august 1 , 2005 .
at december 31 , 2007 , 757123 shares were available for purchase under the 2002 purchase plan .
401 ( k ) plan the company has a 401 ( k ) salary deferral program for eligible employees who have met certain service requirements .
the company matches certain employee contributions ; additional contributions to this plan are at the discretion of the company .
total contribution expense under this plan was $ 5.7 million , $ 5.7 million and $ 5.2 million for the years ended december 31 , 2007 , 2006 and 2005 , respectively. .

Question: Analyse this data from a financial earnings document. what was the percentage change in total contribution expense under the plan between 2006 and 2007?
Choices:
0
-15.9
5.7
0.1
0.0
Correct choice index: 4