Table of Contents Index to Financial Statements 19 approximately 91% of total proved reserves.
The reserves audit for 2014 included a detailed review of eight of our major fields and covered approximately 88% of total proved reserves.
In connection with the 2016 reserves audit, NSAI prepared its own estimates of our proved reserves.
In order to prepare its estimates of proved reserves, NSAI examined our estimates with respect to reserves quantities, future production rates, future net revenue, and the present value of such future net revenue.
NSAI also examined our estimates with respect to reserves categorization, using the definitions for proved reserves set forth in Regulation S-X Rule 4-10(a) and subsequent SEC staff interpretations and guidance.
In the conduct of the reserves audit, NSAI did not independently verify the accuracy and completeness of information and data furnished by us with respect to ownership interests, crude oil and natural gas production, well test data, historical costs of operation and development, product prices, or any agreements relating to current and future operations of the fields and sales of production.
However, if in the course of the examination something came to the attention of NSAI which brought into question the validity or sufficiency of any such information or data, NSAI did not rely on such information or data until it had satisfactorily resolved its questions relating thereto or had independently verified such information or data.
NSAI determined that our estimates of reserves have been prepared in accordance with the definitions and regulations of the SEC, including the criteria of “reasonable certainty,” as it pertains to expectations about the recoverability of reserves in future years, under existing economic and operating conditions, consistent with the definition in Rule 4-10(a)(24) of Regulation S-X.
NSAI issued an unqualified audit opinion on our proved reserves at December 31, 2016, based upon their evaluation.
NSAI concluded that our estimates of proved reserves were, in the aggregate, reasonable and have been prepared in accordance with Standards Pertaining to the Estimating and Auditing of Oil and Gas Reserves Information promulgated by the Society of Petroleum Engineers.
NSAI’s report is attached as Exhibit 99.1 to this Annual Report on Form 10-K.
When compared on a field-by-field basis, some of our estimates are greater and some are less than the estimates of NSAI.
Given the inherent uncertainties and judgments that go into estimating proved reserves, differences between internal and external estimates are to be expected.
For proved reserves at December 31, 2016, on a quantity basis, the NSAI field estimates ranged from 3.1 MMBoe or 2% above to 6 MMBoe or 7% below as compared with our estimates on a field-by-field basis.
Differences between our estimates and those of NSAI are reviewed for accuracy but are not further analyzed unless the aggregate variance is greater than 10%.
Reserves differences at December 31, 2016 were, in the aggregate, approximately 27.9 MMBoe, or 2%.
Proved Reserves We have historically added reserves through our exploration program, development activities, and acquisition of producing properties.
Changes in proved reserves were as follows:
## Table 0 ##
Revisions Revisions of previous estimates represent changes in previous reserves estimates, either upward (positive) or downward (negative), resulting from new information normally obtained from development drilling and production history or resulting from a change in economic factors, such as commodity prices, operating costs, development costs or abandonment costs.
Revisions included the following: ?
changes for the year ended December 31, 2016 include positive revisions of 43 MMBoe for the DJ Basin, 42 MMBoe for the Marcellus Shale, 11 MMBoe for the Permian Basin, 6 MMBoe for deepwater Gulf of Mexico, 5 MMBoe for other onshore US and 10 MMBoe for Alba field, offshore Equatorial Guinea, due to increased performance and/or lower development or operating costs; partially offset by negative revisions of 53 MMBoe due to lower commodity prices; ?
changes for the year ended December 31, 2015 include negative revisions of 307 MMBoe due to lower commodity prices, downward revisions of 9 MMBoe and 5 MMBoe for the DJ Basin and Eagle Ford Shale, respectively, primarily due to current drilling and development plans in the DJ Basin and expected reserve recovery from existing producing wells in the Eagle Ford Shale, and downward revisions of 3 MMBoe due to natural field decline from the Mari-B field,
Average interest-earning deposits with banks, which are primarily maintained with the Federal Reserve Bank, increased significantly in the comparison to the prior year period as we continued to enhance our liquidity position.
Average noninterest-earning assets decreased in 2014 compared with 2013, primarily reflecting lower unsettled securities sales, partially offset by higher investment securities valuation adjustments, both of which are included in noninterest-earning assets for average balance sheet purposes.
Average total deposits increased $10.8 billion in 2014 compared with the prior year, driven by an increase of $12.1 billion in average transaction deposits, which grew to $189 billion in 2014.
Higher average money market deposits, average noninterest-bearing deposits, and average interestbearing demand deposits drove the increase in both commercial and consumer average transaction deposits.
These increases were partially offset by a decrease of $2.6 billion in average retail certificates of deposit attributable to runoff of maturing accounts.
Total deposits at December 31, 2014 were $232.2 billion compared with $220.9 billion at December 31, 2013 and are further discussed within the Consolidated Balance Sheet Review section of this Item 7.
Average total deposits represented 68% of average total assets for 2014 and 69% for 2013.
Average borrowed funds increased in 2014 compared with 2013 primarily due to increases in average Federal Home Loan Bank (FHLB) borrowings, average bank notes and senior debt, and average subordinated debt, in part to enhance our liquidity position.
These increases were partially offset by a decline in average commercial paper.
Total borrowed funds at December 31, 2014 were $56.8 billion compared with $46.1 billion at December 31, 2013 and are further discussed within the Consolidated Balance Sheet Review section of this Item 7.
The Liquidity Risk Management portion of the Risk Management section of this Item 7 includes additional information regarding our borrowed funds.
Business Segment Highlights Total business segment earnings were $3.9 billion in 2014 and $4.0 billion in 2013.
The Business Segments Review section of this Item 7 includes further analysis of our business segment results during 2014 and 2013, including presentation differences from Note 24 Segment Reporting in our Notes To Consolidated Financial Statements in Item 8 of this Report.
Note 24 Segment Reporting presents results of businesses for 2014, 2013 and 2012.
We provide a reconciliation of total business segment earnings to PNC total consolidated net income as reported on a GAAP basis in Note 24 Segment Reporting in our Notes To Consolidated Financial Statements in Item 8 of this Report.
Table 3: Results Of Businesses – Summary
## Table 1 ##
(a) Amounts for 2013 period have been updated to reflect the first quarter 2014 adoption of ASU 2014-01 related to investments in low income housing tax credits.
(b) Period-end balances for BlackRock.
(c) “Other” average assets include investment securities associated with asset and liability management activities.
(d) “Other” includes differences between the total business segment financial results and our total consolidated net income.
Additional detail is included in Note 24 Segment Reporting in the Notes To Consolidated Financial Statements in Item 8 of this Report.
(e) Net income for “Other” in 2014 increased slightly compared to 2013 as lower noninterest expense due to a reduction in benefits costs was mostly offset by lower interest income from investment securities.
Table 32: Change in Nonperforming Assets
## Table 2 ##
(a) New nonperforming assets in the 2013 period include $560 million of loans added in the first quarter of 2013 due to the alignment with interagency supervisory guidance on practices for loans and lines of credit related to consumer lending.
(b) Charge-offs and valuation adjustments in the 2013 period include $134 million of charge-offs due to the alignment with interagency supervisory guidance discussed in footnote (a) above.
The table above presents nonperforming asset activity during 2014 and 2013, respectively.
Nonperforming assets decreased $577 million from $3.5 billion at December 31, 2013 to $2.9 billion at December 31, 2014, as a result of improvements in both consumer and commercial lending.
Consumer lending nonperforming loans decreased $224 million, commercial real estate nonperforming loans declined $184 million and commercial nonperforming loans decreased $167 million.
As of December 31, 2014, approximately 90% of total nonperforming loans were secured by collateral which lessens reserve requirements and is expected to reduce credit losses in the event of default.
As of December 31, 2014, commercial lending nonperforming loans were carried at approximately 65% of their unpaid principal balance, due to charge-offs recorded to date, before consideration of the ALLL.
See Note 3 Asset Quality in the Notes To Consolidated Financial Statements in Item 8 of this Report for additional information on these loans.
Purchased impaired loans are considered performing, even if contractually past due (or if we do not expect to receive payment in full based on the original contractual terms), as we accrete interest income over the expected life of the loans.
The accretable yield represents the excess of the expected cash flows on the loans at the measurement date over the carrying value.
Generally decreases, other than interest rate decreases for variable rate notes, in the net present value of expected cash flows of individual commercial or pooled purchased impaired loans would result in an impairment charge to the provision for credit losses in the period in which the change is deemed probable.
Generally increases in the net present value of expected cash flows of purchased impaired loans would first result in a recovery of previously recorded allowance for loan losses, to the extent applicable, and then an increase to accretable yield for the remaining life of the purchased impaired loans.
Total nonperforming loans and assets in the tables above are significantly lower than they would have been due to this accounting treatment for purchased impaired loans.
This treatment also results in a lower ratio of nonperforming loans to total loans and a higher ratio of ALLL to nonperforming loans.
See Note 4 Purchased Loans in the Notes To Consolidated Financial Statements in Item 8 of this Report for additional information on these loans.
Loan Delinquencies We regularly monitor the level of loan delinquencies and believe these levels may be a key indicator of loan portfolio asset quality.
Measurement of delinquency status is based on the contractual terms of each loan.
Loans that are 30 days or more past due in terms of payment are considered delinquent.
Loan delinquencies exclude loans held for sale and purchased impaired loans, but include government insured or guaranteed loans and loans accounted for under the fair value option.
Total early stage loan delinquencies (accruing loans past due 30 to 89 days) decreased from $1.0 billion at December 31, 2013 to $0.8 billion at December 31, 2014.
The reduction in both consumer and commercial lending early stage delinquencies resulted from improved credit quality.
See Note 1 Accounting Policies in the Notes To Consolidated Financial Statements of this Report for additional information regarding our nonperforming loan and nonaccrual policies.
Accruing loans past due 90 days or more are referred to as late stage delinquencies.
These loans are not included in nonperforming loans and continue to accrue interest because they are well secured by collateral, and/or are in the process of collection, are managed in homogenous portfolios with specified charge-off timeframes adhering to regulatory guidelines, or are certain government insured or guaranteed loans.
These loans decreased $.4 billion, or 26%, from $1.5 billion at December 31, 2013 to $1.1 billion at December 31, 2014, mainly due to a decline in government insured residential real estate loans of $.3 billion, the majority of which we took possession of and conveyed the real estate, or are in the process of conveyance and claim resolution.
The following tables display the delinquency status of our loans at December 31, 2014 and December 31, 2013.
Additional information regarding accruing loans past due is included in Note 3 Asset Quality in the Notes To Consolidated Financial Statements of this Report.

<table><tr><td></td><td colspan="3">Year Ended December 31,</td></tr><tr><td></td><td>2016</td><td>2015</td><td>2014</td></tr><tr><td>(MMBoe)</td><td></td><td></td><td></td></tr><tr><td>Proved Reserves Beginning of Year</td><td>1,421</td><td>1,404</td><td>1,406</td></tr><tr><td>Revisions of Previous Estimates</td><td>64</td><td>-216</td><td>21</td></tr><tr><td>Extensions, Discoveries and Other Additions</td><td>179</td><td>100</td><td>120</td></tr><tr><td>Purchase of Minerals in Place</td><td>4</td><td>269</td><td>—</td></tr><tr><td>Sale of Minerals in Place</td><td>-77</td><td>-6</td><td>-33</td></tr><tr><td>Production</td><td>-154</td><td>-130</td><td>-110</td></tr><tr><td>Proved Reserves End of Year</td><td>1,437</td><td>1,421</td><td>1,404</td></tr></table>
<table><tr><td>Year ended December 31</td><td colspan="2">Net Income (a)</td><td colspan="2">Revenue</td><td colspan="2">Average Assets (a) (b)</td></tr><tr><td>In millions</td><td>2014</td><td>2013</td><td>2014</td><td>2013</td><td>2014</td><td>2013</td></tr><tr><td>Retail Banking</td><td>$728</td><td>$550</td><td>$6,049</td><td>$6,100</td><td>$75,046</td><td>$74,971</td></tr><tr><td>Corporate & Institutional Banking</td><td>2,106</td><td>2,264</td><td>5,476</td><td>5,506</td><td>122,927</td><td>112,970</td></tr><tr><td>Asset Management Group</td><td>181</td><td>162</td><td>1,107</td><td>1,040</td><td>7,745</td><td>7,366</td></tr><tr><td>Residential Mortgage Banking</td><td>35</td><td>148</td><td>800</td><td>1,100</td><td>7,857</td><td>9,896</td></tr><tr><td>BlackRock</td><td>530</td><td>469</td><td>703</td><td>621</td><td>6,640</td><td>6,272</td></tr><tr><td>Non-Strategic Assets Portfolio</td><td>367</td><td>379</td><td>587</td><td>742</td><td>8,338</td><td>9,987</td></tr><tr><td>Total business segments</td><td>3,947</td><td>3,972</td><td>14,722</td><td>15,109</td><td>228,553</td><td>221,462</td></tr><tr><td>Other (c) (d) (e)</td><td>260</td><td>240</td><td>653</td><td>903</td><td>99,300</td><td>84,202</td></tr><tr><td>Total</td><td>$4,207</td><td>$4,212</td><td>$15,375</td><td>$16,012</td><td>$327,853</td><td>$305,664</td></tr></table>
<table><tr><td>In millions</td><td>2014</td><td>2013</td></tr><tr><td>January 1</td><td>$3,457</td><td>$3,794</td></tr><tr><td>New nonperforming assets (a)</td><td>2,127</td><td>3,343</td></tr><tr><td>Charge-offs and valuation adjustments (b)</td><td>-585</td><td>-1,002</td></tr><tr><td>Principal activity, including paydowns and payoffs</td><td>-1,001</td><td>-1,016</td></tr><tr><td>Asset sales and transfers to loans held for sale</td><td>-570</td><td>-492</td></tr><tr><td>Returned to performing status</td><td>-548</td><td>-1,170</td></tr><tr><td>December 31</td><td>$2,880</td><td>$3,457</td></tr></table>

Question: by how much , in billions , did early stage loans decrease between dec 31 2013 and dec 31 2014?