investment policy , which is described more fully in note 15 employee benefit plans in the notes to consolidated financial statements in item 8 of this report . we calculate the expense associated with the pension plan and the assumptions and methods that we use include a policy of reflecting trust assets at their fair market value . on an annual basis , we review the actuarial assumptions related to the pension plan , including the discount rate , the rate of compensation increase and the expected return on plan assets . the discount rate and compensation increase assumptions do not significantly affect pension expense . however , the expected long-term return on assets assumption does significantly affect pension expense . our expected long- term return on plan assets for determining net periodic pension expense has been 8.25% ( 8.25 % ) for the past three years . the expected return on plan assets is a long-term assumption established by considering historical and anticipated returns of the asset classes invested in by the pension plan and the allocation strategy currently in place among those classes . while this analysis gives appropriate consideration to recent asset performance and historical returns , the assumption represents a long-term prospective return . we review this assumption at each measurement date and adjust it if warranted . for purposes of setting and reviewing this assumption , 201clong- term 201d refers to the period over which the plan 2019s projected benefit obligation will be disbursed . while year-to-year annual returns can vary significantly ( rates of return for the reporting years of 2009 , 2008 , and 2007 were +20.61% ( +20.61 % ) , -32.91% ( -32.91 % ) , and +7.57% ( +7.57 % ) , respectively ) , the assumption represents our estimate of long-term average prospective returns . our selection process references certain historical data and the current environment , but primarily utilizes qualitative judgment regarding future return expectations . recent annual returns may differ but , recognizing the volatility and unpredictability of investment returns , we generally do not change the assumption unless we modify our investment strategy or identify events that would alter our expectations of future returns . to evaluate the continued reasonableness of our assumption , we examine a variety of viewpoints and data . various studies have shown that portfolios comprised primarily of us equity securities have returned approximately 10% ( 10 % ) over long periods of time , while us debt securities have returned approximately 6% ( 6 % ) annually over long periods . application of these historical returns to the plan 2019s allocation of equities and bonds produces a result between 8% ( 8 % ) and 8.5% ( 8.5 % ) and is one point of reference , among many other factors , that is taken into consideration . we also examine the plan 2019s actual historical returns over various periods . recent experience is considered in our evaluation with appropriate consideration that , especially for short time periods , recent returns are not reliable indicators of future returns , and in many cases low returns in recent time periods are followed by higher returns in future periods ( and vice versa ) . acknowledging the potentially wide range for this assumption , we also annually examine the assumption used by other companies with similar pension investment strategies , so that we can ascertain whether our determinations markedly differ from other observers . in all cases , however , this data simply informs our process , which places the greatest emphasis on our qualitative judgment of future investment returns , given the conditions existing at each annual measurement date . the expected long-term return on plan assets for determining net periodic pension cost for 2009 was 8.25% ( 8.25 % ) , unchanged from 2008 . during 2010 , we intend to decrease the midpoint of the plan 2019s target allocation range for equities by approximately five percentage points . as a result of this change and taking into account all other factors described above , pnc will change the expected long-term return on plan assets to 8.00% ( 8.00 % ) for determining net periodic pension cost for 2010 . under current accounting rules , the difference between expected long-term returns and actual returns is accumulated and amortized to pension expense over future periods . each one percentage point difference in actual return compared with our expected return causes expense in subsequent years to change by up to $ 8 million as the impact is amortized into results of operations . the table below reflects the estimated effects on pension expense of certain changes in annual assumptions , using 2010 estimated expense as a baseline . change in assumption ( a ) estimated increase to 2010 pension expense ( in millions ) .
the decrease in pretax pension expenses was what percentage of a decrease?
( a ) the impact is the effect of changing the specified assumption while holding all other assumptions constant . we currently estimate a pretax pension expense of $ 41 million in 2010 compared with pretax expense of $ 117 million in 2009 . this year-over-year reduction was primarily due to the amortization impact of the favorable 2009 investment returns as compared with the expected long-term return assumption . our pension plan contribution requirements are not particularly sensitive to actuarial assumptions . investment performance has the most impact on contribution requirements and will drive the amount of permitted contributions in future years . also , current law , including the provisions of the pension protection act of 2006 , sets limits as to both minimum and maximum contributions to the plan . we expect that the minimum required contributions under the law will be zero for 2010 . we maintain other defined benefit plans that have a less significant effect on financial results , including various .