THE GOLDMAN SACHS GROUP, INC.  AND SUBSIDIARIES Notes to Consolidated Financial Statements ‰ Purchased interests represent senior and subordinated interests, purchased in connection with secondary market-making activities, in securitization entities in which the firm also holds retained interests.
‰ Substantially all of the total outstanding principal amount and total retained interests relate to securitizations during 2014 and thereafter as of December 2018, and relate to securitizations during 2012 and thereafter as of December 2017.
‰ The fair value of retained interests was $3.28 billion as of December 2018 and $2.13 billion as of December 2017.
In addition to the interests in the table above, the firm had other continuing involvement in the form of derivative transactions and commitments with certain nonconsolidated VIEs.
The carrying value of these derivatives and commitments was a net asset of $75 million as of December 2018 and $86 million as of December 2017, and the notional amount of these derivatives and commitments was $1.09 billion as of December 2018 and $1.26 billion as of December 2017.
The notional amounts of these derivatives and commitments are included in maximum exposure to loss in the nonconsolidated VIE table in Note 12.
The table below presents information about the weighted average key economic assumptions used in measuring the fair value of mortgage-backed retained interests.
## Table 0 ##
In the table above: ‰ Amounts do not reflect the benefit of other financial instruments that are held to mitigate risks inherent in these retained interests.
‰ Changes in fair value based on an adverse variation in assumptions generally cannot be extrapolated because the relationship of the change in assumptions to the change in fair value is not usually linear.
‰ The impact of a change in a particular assumption is calculated independently of changes in any other assumption.
In practice, simultaneous changes in assumptions might magnify or counteract the sensitivities disclosed above.
‰ The constant prepayment rate is included only for positions for which it is a key assumption in the determination of fair value.
‰ The discount rate for retained interests that relate to U. S.  government agency-issued collateralized mortgage obligations does not include any credit loss.
Expected credit loss assumptions are reflected in the discount rate for the remainder of retained interests.
The firm has other retained interests not reflected in the table above with a fair value of $133 million and a weighted average life of 4.2 years as of December 2018, and a fair value of $56 million and a weighted average life of 4.5 years as of December 2017.
Due to the nature and fair value of certain of these retained interests, the weighted average assumptions for constant prepayment and discount rates and the related sensitivity to adverse changes are not meaningful as of both December 2018 and December 2017.
The firm’s maximum exposure to adverse changes in the value of these interests is the carrying value of $133 million as of December 2018 and $56 million as of December 2017.
Note 12.
Variable Interest Entities A variable interest in a VIE is an investment (e. g. , debt or equity) or other interest (e. g. , derivatives or loans and lending commitments) that will absorb portions of the VIE’s expected losses and/or receive portions of the VIE’s expected residual returns.
The firm’s variable interests in VIEs include senior and subordinated debt; loans and lending commitments; limited and general partnership interests; preferred and common equity; derivatives that may include foreign currency, equity and/or credit risk; guarantees; and certain of the fees the firm receives from investment funds.
Certain interest rate, foreign currency and credit derivatives the firm enters into with VIEs are not variable interests because they create, rather than absorb, risk.
VIEs generally finance the purchase of assets by issuing debt and equity securities that are either collateralized by or indexed to the assets held by the VIE.
The debt and equity securities issued by a VIE may include tranches of varying levels of subordination.
The firm’s involvement with VIEs includes securitization of financial assets, as described in Note 11, and investments in and loans to other types of VIEs, as described below.
See Note 11 for further information about securitization activities, including the definition of beneficial interests.
See Note 3 for the firm’s consolidation policies, including the definition of a VIE.
The completion factor method is used for the months of incurred claims prior to the most recent three months because the historical percentage of claims processed for those months is at a level sufficient to produce a consistently reliable result.
Conversely, for the most recent three months of incurred claims, the volume of claims processed historically is not at a level sufficient to produce a reliable result, which therefore requires us to examine historical trend patterns as the primary method of evaluation.
Medical cost trends potentially are more volatile than other segments of the economy.
The drivers of medical cost trends include increases in the utilization of hospital and physician services, prescription drugs, and new medical technologies, as well as the inflationary effect on the cost per unit of each of these expense components.
Other external factors such as government-mandated benefits or other regulatory changes, catastrophes, and epidemics also may impact medical cost trends.
Additionally, as we realign our commercial strategy, we continue to reduce the level of traditional utilization management functions such as preauthorization of services, monitoring of inpatient admissions, and requirements for physician referrals.
Other internal factors such as system conversions and claims processing interruptions also may impact our ability to accurately predict estimates of historical completion factors or medical cost trends.
All of these factors are considered in estimating IBNR and in estimating the per member per month claims trend for purposes of determining the reserve for the most recent three months.
Each of these factors requires significant judgment by management.
The completion and claims per member per month trend factors are the most significant factors impacting the IBNR estimate.
The following table illustrates the sensitivity of these factors and the estimated potential impact on our operating results caused by changes in these factors based on December 31, 2003 data:
## Table 1 ##
(a) Reflects estimated potential changes in medical and other expenses payable caused by changes in completion factors for incurred months prior to the most recent three months.
(b) Reflects estimated potential changes in medical and other expenses payable caused by changes in annualized claims trend used for the estimation of per member per month incurred claims for the most recent three months.
Most medical claims are paid within a few months of the member receiving service from a physician or other health care provider.
As a result, these liabilities generally are described as having a “short-tail”, which causes less than 2% of our medical and other expenses payable as of the end of any given period to be outstanding for more than 12 months.
As such, we expect that substantially all of the 2003 estimate of medical and other expenses payable will be known and paid during 2004.
Our reserving practice is to consistently recognize the actuarial best point estimate within a level of confidence required by actuarial standards.
Actuarial standards of practice generally require a level of confidence such that the liabilities established for IBNR have a greater probability of being adequate versus being insufficient, or such that the liabilities established for IBNR are sufficient to cover obligations under an assumption of moderately adverse conditions.
Adverse conditions are situations in which the actual claims are
TRICARE change orders occur when we perform services or incur costs under the directive of the federal government that were not originally specified in our contracts.
Under federal regulations we are entitled to an equitable adjustment to the contract price, which results in additional premium revenues.
Examples of items that have necessitated substantial change orders in recent years include congressionally legislated increases in the level of benefits for TRICARE beneficiaries and the administration of new government programs such as TRICARE for Life and TRICARE Senior Pharmacy.
Like BPAs, we record revenue applicable to change orders when these amounts are determinable and the collectibility is reasonably assured.
Unlike BPAs, where settlement only occurs at specified intervals, change orders may be negotiated and settled at any time throughout the year.
Total TRICARE premium and ASO fee receivables were as follows at December 31, 2003 and 2002:
## Table 2 ##
Our TRICARE contracts also contain risk-sharing provisions with the federal government to minimize any losses and limit any profits in the event that medical costs for which we are at risk differ from the levels targeted in our contracts.
Amounts receivable from the federal government under such risk-sharing provisions are included in the BPA receivable above, while amounts payable to the federal government under these provisions of approximately $17.3 million at December 31, 2003 are included in medical and other expenses payable in our consolidated balance sheets.
Investment Securities Investment securities totaled $1,995.8 million, or 38% of total assets at December 31, 2003.
Debt securities totaled $1,960.6 million, or 98% of our total investment portfolio.
More than 94% of our debt securities were of investment-grade quality, with an average credit rating of AA by Standard & Poor’s at December 31, 2003.
Most of the debt securities that are below investment grade are rated at the higher end (B or better) of the noninvestment grade spectrum.
Our investment policy limits investments in a single issuer and requires diversification among various asset types.
Duration is indicative of the relationship between changes in market value to changes in interest rates, providing a general indication of the sensitivity of the fair values of our debt securities to changes in interest rates.
However, actual market values may differ significantly from estimates based on duration.
The average duration of our debt securities was approximately 3.5 years at December 31, 2003.
Based on this duration, a 1% increase in interest rates would generally decrease the fair value of our debt securities by approximately $70 million.
Our investment securities are categorized as available for sale and, as a result, are stated at fair value.
Fair value of publicly traded debt and equity securities are based on quoted market prices.
Non-traded debt securities are priced independently by a third party vendor.
Fair value of venture capital debt securities that are privately
Revenue for other healthcare services is recognized on a fee-for-service basis at estimated collectible amounts at the time services are rendered.
Our fees are determined in advance for each type of service performed.
Investment Securities Investment securities totaled $9.8 billion, or 47.3% of total assets at December 31, 2013, and $9.8 billion, or 49% of total assets at December 31, 2012.
Debt securities, detailed below, comprised this entire investment portfolio at December 31, 2013 and at December 31, 2012.
The fair value of debt securities were as follows at December 31, 2013 and 2012:

Tables referenced above, in order (Table 0 first):
<table><tr><td></td><td>As of December</td></tr><tr><td><i>$ in millions</i></td><td>2018</td><td>2017</td></tr><tr><td>Fair value of retained interests</td><td>$ 3,151</td><td>$2,071</td></tr><tr><td>Weighted average life (years)</td><td>7.2</td><td>6.0</td></tr><tr><td>Constant prepayment rate</td><td>11.9%</td><td>9.4%</td></tr><tr><td>Impact of 10% adverse change</td><td>$ -27</td><td>$ -19</td></tr><tr><td>Impact of 20% adverse change</td><td>$ -53</td><td>$ -35</td></tr><tr><td>Discount rate</td><td>4.7%</td><td>4.2%</td></tr><tr><td>Impact of 10% adverse change</td><td>$ -75</td><td>$ -35</td></tr><tr><td>Impact of 20% adverse change</td><td>$ -147</td><td>$ -70</td></tr></table>
<table><tr><td colspan="2">Completion Factor (a):</td><td colspan="2">Claims Trend Factor (b):</td></tr><tr><td> (Decrease) Increase in Factor</td><td>Increase (Decrease) in Medical and Other Expenses Payable</td><td>(Decrease) Increase in Factor</td><td>Increase (Decrease) in Medical and Other Expenses Payable</td></tr><tr><td colspan="4">(dollars in thousands)</td></tr><tr><td>-3%</td><td>$136,000</td><td>-3%</td><td>$-59,000</td></tr><tr><td>-2%</td><td>$88,000</td><td>-2%</td><td>$-41,000</td></tr><tr><td>-1%</td><td>$43,000</td><td>-1%</td><td>$-22,000</td></tr><tr><td>1%</td><td>$-40,000</td><td>1%</td><td>$14,000</td></tr><tr><td>2%</td><td>$-79,000</td><td>2%</td><td>$33,000</td></tr><tr><td>3%</td><td>$-116,000</td><td>3%</td><td>$51,000</td></tr></table>
<table><tr><td></td><td>2003</td><td>2002</td></tr><tr><td></td><td colspan="2">(in thousands)</td></tr><tr><td>TRICARE premiums receivable:</td><td></td><td></td></tr><tr><td>Base receivable</td><td>$254,688</td><td>$190,339</td></tr><tr><td>Bid price adjustments (BPAs)</td><td>92,875</td><td>104,044</td></tr><tr><td>Change orders</td><td>7,073</td><td>1,400</td></tr><tr><td>Subtotal</td><td>354,636</td><td>295,783</td></tr><tr><td>Less: long-term portion of BPAs</td><td>-38,794</td><td>-86,471</td></tr><tr><td>Total TRICARE premiums receivable</td><td>$315,842</td><td>$209,312</td></tr><tr><td>TRICARE ASO fees receivable:</td><td></td><td></td></tr><tr><td>Base receivable</td><td>$—</td><td>$7,205</td></tr><tr><td>Change orders</td><td>11,968</td><td>56,230</td></tr><tr><td>Total TRICARE ASO fees receivable</td><td>$11,968</td><td>$63,435</td></tr></table>

Question: what was the change in fair value of retained interests in billions as of december 2018 and december 2017?
Answer: 1.15
Reasoning program: subtract(3.28,2.13)