NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued) Note 2—Financial Instruments (Continued) The following table shows the notional principal, net fair value, and credit risk amounts of the Company’s foreign currency instruments as of September 29, 2007 and September 30, 2006 (in millions):
## Table 0 ##
The notional principal amounts for derivative instruments provide one measure of the transaction volume outstanding as of year-end, and do not represent the amount of the Company’s exposure to credit or market loss.
The credit risk amounts shown in the table above represents the Company’s gross exposure to potential accounting loss on these transactions if all counterparties failed to perform according to the terms of the contract, based on then-current currency exchange rates at each respective date.
The Company’s exposure to credit loss and market risk will vary over time as a function of currency exchange rates.
The estimates of fair value are based on applicable and commonly used pricing models and prevailing financial market information as of September 29, 2007 and September 30, 2006.
Although the table above reflects the notional principal, fair value, and credit risk amounts of the Company’s foreign exchange instruments, it does not reflect the gains or losses associated with the exposures and transactions that the foreign exchange instruments are intended to hedge.
The amounts ultimately realized upon settlement of these financial instruments, together with the gains and losses on the underlying exposures, will depend on actual market conditions during the remaining life of the instruments.
Foreign Exchange Risk Management The Company may enter into foreign currency forward and option contracts with financial institutions to protect against foreign exchange risk associated with existing assets and liabilities, certain firmly committed transactions, forecasted future cash flows, and net investments in foreign subsidiaries.
Generally, the Company’s practice is to hedge a majority of its material foreign exchange exposures.
However, the Company may choose not to hedge certain foreign exchange exposures due to immateriality, prohibitive economic cost of hedging particular exposures, or limited availability of appropriate hedging instruments.
To help protect gross margins from fluctuations in foreign currency exchange rates, the Company’s U. S.  dollar functional subsidiaries hedge a portion of forecasted foreign currency revenue, and the Company’s non-U.
S.  dollar functional subsidiaries selling in local currencies hedge a portion of forecasted inventory purchases not denominated in the subsidiaries’ functional currency.
Other comprehensive income associated with hedges of foreign currency revenue is recognized as a component of net sales in the same period as the related sales are recognized, and other comprehensive income related to inventory purchases is recognized as a component of cost of sales in the same period as the related costs are recognized.
Table IV Allowance for Credit Losses (continued)
## Table 1 ##
(6) Loan and allowance ratios for 2016 include $243 million of non-U.
S.  credit card allowance for loan and lease losses and $9.2 billion of ending non-U.
S.  credit card loans, which were included in assets of business held for sale on the Consolidated Balance Sheet at December 31, 2016.
See footnote 1 for more information.
(7) Outstanding loan and lease balances and ratios do not include loans accounted for under the fair value option of $5.7 billion, $7.1 billion, $6.9 billion, $8.7 billion and $10.0 billion at December 31, 2017, 2016, 2015, 2014 and 2013, respectively.
Average loans accounted for under the fair value option were $6.7 billion, $8.2 billion, $7.7 billion, $9.9 billion and $9.5 billion in 2017, 2016, 2015, 2014 and 2013, respectively.
(8) Excludes consumer loans accounted for under the fair value option of $928 million, $1.1 billion, $1.9 billion, $2.1 billion and $2.2 billion at December 31, 2017, 2016, 2015, 2014 and 2013, respectively.
(9) Excludes commercial loans accounted for under the fair value option of $4.8 billion, $6.0 billion, $5.1 billion, $6.6 billion and $7.9 billion at December 31, 2017, 2016, 2015, 2014 and 2013, respectively.
(10) Net charge-offs exclude $207 million, $340 million, $808 million, $810 million and $2.3 billion of write-offs in the PCI loan portfolio in 2017, 2016, 2015, 2014 and 2013 respectively.
For more information on PCI write-offs, see Consumer Portfolio Credit Risk Management – Purchased Credit-impaired Loan Portfolio on page 76.
(11) For more information on our definition of nonperforming loans, see page 78 and page 83.
(12) Primarily includes amounts allocated to U. S.  credit card and unsecured consumer lending portfolios in Consumer Banking, PCI loans and the non-U.
S.  credit portfolio in All Other.
(13) For more information on the PCI loan portfolio and the valuation allowance for PCI loans, see Note 4 – Outstanding Loans and Leases and Note 5 – Allowance for Credit Losses to the Consolidated Financial Statements.
The portion of compensation expense associated with certain long-term incentive plans (“LTIP”) funded or to be funded through share distributions to participants of BlackRock stock held by PNC and a Merrill Lynch & Co. , Inc.  (“Merrill Lynch”) cash compensation contribution, has been excluded because it ultimately does not impact BlackRock’s book value.
The expense related to the Merrill Lynch cash compensation contribution ceased at the end of third quarter 2011.
As of first quarter 2012, all of the Merrill Lynch contributions had been received.
Compensation expense associated with appreciation (depreciation) on investments related to certain BlackRock deferred compensation plans has been excluded as returns on investments set aside for these plans, which substantially offset this expense, are reported in non-operating income (expense).
Management believes operating income exclusive of these items is a useful measure in evaluating BlackRock’s operating performance and helps enhance the comparability of this information for the reporting periods presented.
Operating margin, as adjusted: Operating income used for measuring operating margin, as adjusted, is equal to operating income, as adjusted, excluding the impact of closed-end fund launch costs and commissions.
Management believes the exclusion of such costs and commissions is useful because these costs can fluctuate considerably and revenues associated with the expenditure of these costs will not fully impact the Company’s results until future periods.
Operating margin, as adjusted, allows the Company to compare performance from period-to-period by adjusting for items that may not recur, recur infrequently or may have an economic offset in non-operating income (expense).
Examples of such adjustments include BGI transaction and integration costs, U. K.  lease exit costs, contribution to STIFs, restructuring charges, closed-end fund launch costs, commissions paid to certain employees as compensation and fluctuations in compensation expense based on mark-to-market movements in investments held to fund certain compensation plans.
The Company also uses operating margin, as adjusted, to monitor corporate performance and efficiency and as a benchmark to compare its performance with other companies.
Management uses both the GAAP and nonGAAP financial measures in evaluating the financial performance of BlackRock.
The non-GAAP measure by itself may pose limitations because it does not include all of the Company’s revenues and expenses.
Revenue used for operating margin, as adjusted, excludes distribution and servicing costs paid to related parties and other third parties.
Management believes the exclusion of such costs is useful because it creates consistency in the treatment for certain contracts for similar services, which due to the terms of the contracts, are accounted for under GAAP on a net basis within investment advisory, administration fees and securities lending revenue.
Amortization of deferred sales commissions is excluded from revenue used for operating margin measurement, as adjusted, because such costs, over time, substantially offset distribution fee revenue earned by the Company.
For each of these items, BlackRock excludes from revenue used for operating margin, as adjusted, the costs related to each of these items as a proxy for such offsetting revenues.
(b) Non-operating income (expense), less net income (loss) attributable to non-controlling interests, as adjusted: Non-operating income (expense), less net income (loss) attributable to NCI, as adjusted, is presented below.
The compensation expense offset is recorded in operating income.
This compensation expense has been included in non-operating income (expense), less net income (loss) attributable to NCI, as adjusted, to offset returns on investments set aside for these plans, which are reported in non-operating income (expense), GAAP basis.
## Table 2 ##
(1) Net of net income (loss) attributable to NCI.
Management believes non-operating income (expense), less net income (loss) attributable to NCI, as adjusted, provides comparability of this information among reporting periods and is an effective measure for reviewing BlackRock’s non-operating contribution to its results.
As compensation expense associated with (appreciation) depreciation on investments related to certain deferred compensation plans, which is included in operating income, substantially offsets the gain (loss) on the investments set aside for these plans, management
IRON MOUNTAIN INCORPORATED NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued) DECEMBER 31, 2017 (In thousands, except share and per share data) 2.
Summary of Significant Accounting Policies (Continued) 100 Entities are required to record the fair value of a liability for an asset retirement obligation in the period in which it is incurred.
Asset retirement obligations represent the costs to replace or remove tangible long-lived assets required by law, regulatory rule or contractual agreement.
When the liability is initially recorded, the entity capitalizes the cost by increasing the carrying amount of the related long-lived asset, which is then depreciated over the useful life of the related asset.
The liability is increased over time through accretion expense (included in depreciation expense) such that the liability will equate to the future cost to retire the long-lived asset at the expected retirement date.
Upon settlement of the liability, an entity either settles the obligation for its recorded amount or realizes a gain or loss upon settlement.
Our asset retirement obligations are primarily the result of requirements under our facility lease agreements which generally have "return to original condition" clauses which would require us to remove or restore items such as shred pits, vaults, demising walls and office build-outs, among others.
The significant assumptions used in estimating our aggregate asset retirement obligation are the timing of removals, the probability of a requirement to perform, estimated cost and associated expected inflation rates that are consistent with historical rates and credit-adjusted risk-free rates that approximate our incremental borrowing rate.
A reconciliation of liabilities for asset retirement obligations (included in other long-term liabilities) is as follows:

<table><tr><td> </td><td colspan="3"> September 29, 2007</td><td colspan="3"> September 30, 2006</td></tr><tr><td> </td><td> Notional Principal</td><td>Fair Value</td><td> Credit Risk Amounts</td><td> Notional Principal</td><td>Fair Value</td><td> Credit Risk Amounts</td></tr><tr><td>Foreign exchange instruments qualifying as accounting hedges:</td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td> Spot/Forward contracts</td><td>$570</td><td>$-8</td><td>$—</td><td>$351</td><td>$6</td><td>$6</td></tr><tr><td>Purchased options</td><td>$2,564</td><td>$10</td><td>$10</td><td>$1,256</td><td>$9</td><td>$9</td></tr><tr><td>Sold options</td><td>$1,498</td><td>$-2</td><td>$—</td><td>$80</td><td>$-1</td><td>$—</td></tr><tr><td> Foreign exchange instruments other than accounting hedges:</td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td> Spot/Forward contracts</td><td>$1,768</td><td>$-2</td><td>$—</td><td>$1,103</td><td>$2</td><td>$2</td></tr><tr><td>Purchased options</td><td>$161</td><td>$1</td><td>$1</td><td>$167</td><td>$1</td><td>$—</td></tr></table>
<table><tr><td>(Dollars in millions)</td><td>2017</td><td>2016</td><td>2015</td><td>2014</td><td>2013</td></tr><tr><td>Loan and allowance ratios<sup>-6</sup>:</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Loans and leases outstanding at December 31<sup>-7</sup></td><td>$931,039</td><td>$908,812</td><td>$890,045</td><td>$867,422</td><td>$918,191</td></tr><tr><td>Allowance for loan and lease losses as a percentage of total loans and leases outstanding at December 31<sup>-7</sup></td><td>1.12%</td><td>1.26%</td><td>1.37%</td><td>1.66%</td><td>1.90%</td></tr><tr><td>Consumer allowance for loan and lease losses as a percentage of total consumer loans and leases outstanding at December 31<sup>-8</sup></td><td>1.18</td><td>1.36</td><td>1.63</td><td>2.05</td><td>2.53</td></tr><tr><td>Commercial allowance for loan and lease losses as a percentage of total commercial loans and leases outstanding at December 31<sup>-9</sup></td><td>1.05</td><td>1.16</td><td>1.11</td><td>1.16</td><td>1.03</td></tr><tr><td>Average loans and leases outstanding<sup>-7</sup></td><td>$911,988</td><td>$892,255</td><td>$869,065</td><td>$888,804</td><td>$909,127</td></tr><tr><td>Net charge-offs as a percentage of average loans and leases outstanding<sup>-7, 10</sup></td><td>0.44%</td><td>0.43%</td><td>0.50%</td><td>0.49%</td><td>0.87%</td></tr><tr><td>Net charge-offs and PCI write-offs as a percentage of average loans and leases outstanding<sup>-7</sup></td><td>0.46</td><td>0.47</td><td>0.59</td><td>0.58</td><td>1.13</td></tr><tr><td>Allowance for loan and lease losses as a percentage of total nonperforming loans and leases at December 31<sup>-7, 11</sup></td><td>161</td><td>149</td><td>130</td><td>121</td><td>102</td></tr><tr><td>Ratio of the allowance for loan and lease losses at December 31 to net charge-offs<sup>-10</sup></td><td>2.61</td><td>3.00</td><td>2.82</td><td>3.29</td><td>2.21</td></tr><tr><td>Ratio of the allowance for loan and lease losses at December 31 to net charge-offs and PCI write-offs</td><td>2.48</td><td>2.76</td><td>2.38</td><td>2.78</td><td>1.70</td></tr><tr><td>Amounts included in allowance for loan and lease losses for loans and leases that are excluded from nonperforming loans and leases at December 31<sup>-12</sup></td><td>$3,971</td><td>$3,951</td><td>$4,518</td><td>$5,944</td><td>$7,680</td></tr><tr><td>Allowance for loan and lease losses as a percentage of total nonperforming loans and leases, excluding the allowance for loan and lease losses for loans and leases that are excluded from nonperforming loans and leases at December 31<sup>-7, 12</sup></td><td>99%</td><td>98%</td><td>82%</td><td>71%</td><td>57%</td></tr><tr><td>Loan and allowance ratios excluding PCI loans and the related valuation allowance<sup>-6, 13</sup>:</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Allowance for loan and lease losses as a percentage of total loans and leases outstanding at December 31<sup>-7</sup></td><td>1.10%</td><td>1.24%</td><td>1.31%</td><td>1.51%</td><td>1.67%</td></tr><tr><td>Consumer allowance for loan and lease losses as a percentage of total consumer loans and leases outstanding at December 31<sup>-8</sup></td><td>1.15</td><td>1.31</td><td>1.50</td><td>1.79</td><td>2.17</td></tr><tr><td>Net charge-offs as a percentage of average loans and leases outstanding<sup>-7</sup></td><td>0.44</td><td>0.44</td><td>0.51</td><td>0.50</td><td>0.90</td></tr><tr><td>Allowance for loan and lease losses as a percentage of total nonperforming loans and leases at December 31<sup>-7, 11</sup></td><td>156</td><td>144</td><td>122</td><td>107</td><td>87</td></tr><tr><td>Ratio of the allowance for loan and lease losses at December 31 to net charge-offs</td><td>2.54</td><td>2.89</td><td>2.64</td><td>2.91</td><td>1.89</td></tr></table>
<table><tr><td><i>(Dollar amounts in millions)</i></td><td>2012</td><td>2011</td><td>2010</td></tr><tr><td>Non-operating income (expense), GAAP basis</td><td>$-54</td><td>$-114</td><td>$23</td></tr><tr><td>Less: Net income (loss) attributable to NCI</td><td>-18</td><td>2</td><td>-13</td></tr><tr><td>Non-operating income (expense)<sup>(1)</sup></td><td>-36</td><td>-116</td><td>36</td></tr><tr><td>Compensation expense related to (appreciation) depreciation on deferred compensation plans</td><td>-6</td><td>3</td><td>-11</td></tr><tr><td>Non-operating income (expense), less net income (loss) attributable to NCI, as adjusted</td><td>$-42</td><td>$-113</td><td>$25</td></tr></table>

Question: What's the difference of average loans and leases between 2016 and 2017? (in million)
Answer: 19733