discount rate 2014the assumed discount rate is used to determine the current retirement related benefit plan expense and obligations , and represents the interest rate that is used to determine the present value of future cash flows currently expected to be required to effectively settle a plan 2019s benefit obligations . the discount rate assumption is determined for each plan by constructing a portfolio of high quality bonds with cash flows that match the estimated outflows for future benefit payments to determine a single equivalent discount rate . benefit payments are not only contingent on the terms of a plan , but also on the underlying participant demographics , including current age , and assumed mortality . we use only bonds that are denominated in u.s . dollars , rated aa or better by two of three nationally recognized statistical rating agencies , have a minimum outstanding issue of $ 50 million as of the measurement date , and are not callable , convertible , or index linked . since bond yields are generally unavailable beyond 30 years , we assume those rates will remain constant beyond that point . taking into consideration the factors noted above , our weighted average discount rate for pensions was 5.23% ( 5.23 % ) and 5.84% ( 5.84 % ) , as of december 31 , 2011 and 2010 , respectively . our weighted average discount rate for other postretirement benefits was 4.94% ( 4.94 % ) and 5.58% ( 5.58 % ) as of december 31 , 2011 and 2010 , respectively . expected long-term rate of return 2014the expected long-term rate of return on assets is used to calculate net periodic expense , and is based on such factors as historical returns , targeted asset allocations , investment policy , duration , expected future long-term performance of individual asset classes , inflation trends , portfolio volatility , and risk management strategies . while studies are helpful in understanding current trends and performance , the assumption is based more on longer term and prospective views . in order to reflect expected lower future market returns , we have reduced the expected long-term rate of return assumption from 8.50% ( 8.50 % ) , used to record 2011 expense , to 8.00% ( 8.00 % ) for 2012 . the decrease in the expected return on assets assumption is primarily related to lower bond yields and updated return assumptions for equities . unless plan assets and benefit obligations are subject to remeasurement during the year , the expected return on pension assets is based on the fair value of plan assets at the beginning of the year . an increase or decrease of 25 basis points in the discount rate and the expected long-term rate of return assumptions would have had the following approximate impacts on pensions : ( $ in millions ) increase ( decrease ) in 2012 expense increase ( decrease ) in december 31 , 2011 obligations .

Table:
( $ in millions ) | increase ( decrease ) in 2012 expense | increase ( decrease ) in december 31 2011 obligations
25 basis point decrease in discount rate | $ 18 | $ 146
25 basis point increase in discount rate | -17 ( 17 ) | -154 ( 154 )
25 basis point decrease in expected return on assets | 8 | n.a .
25 basis point increase in expected return on assets | -8 ( 8 ) | n.a .
differences arising from actual experience or changes in assumptions might materially affect retirement related benefit plan obligations and the funded status .
actuarial gains and losses arising from differences from actual experience or changes in assumptions are deferred in accumulated other comprehensive income .
this unrecognized amount is amortized to the extent it exceeds 10% ( 10 % ) of the greater of the plan 2019s benefit obligation or plan assets .
the amortization period for actuarial gains and losses is the estimated average remaining service life of the plan participants , which is approximately 10 years .
cas expense 2014in addition to providing the methodology for calculating retirement related benefit plan costs , cas also prescribes the method for assigning those costs to specific periods .
while the ultimate liability for such costs under fas and cas is similar , the pattern of cost recognition is different .
the key drivers of cas pension expense include the funded status and the method used to calculate cas reimbursement for each of our plans as well as our expected long-term rate of return on assets assumption .
unlike fas , cas requires the discount rate to be consistent with the expected long-term rate of return on assets assumption , which changes infrequently given its long-term nature .
as a result , changes in bond or other interest rates generally do not impact cas .
in addition , unlike under fas , we can only allocate pension costs for a plan under cas until such plan is fully funded as determined under erisa requirements .
other fas and cas considerations 2014we update our estimates of future fas and cas costs at least annually based on factors such as calendar year actual plan asset returns , final census data from the end of the prior year , and other actual and projected experience .
a key driver of the difference between fas and cas expense ( and consequently , the fas/cas adjustment ) is the pattern of earnings and expense recognition for gains and losses that arise when our asset and liability experiences differ from our assumptions under each set of requirements .
under fas , our net gains and losses exceeding the 10% ( 10 % ) corridor are amortized .

Question: what is the percentage change in the weighted average discount rate for other post-retirement benefits from 2010 to 2011?
Answer: -11.5%
Calculation: subtract(4.94, 5.58), divide(#0, 5.58)