The following table summarizes the changes in the fair value of the pension plan assets classified as Level 3 in the fair value hierarchy for each of the years ended December 31, 2011,and 2010:
## Table 0 ##
The following table sets forth, by level within the fair value hierarchy discussed in Note 8 – Fair Value Measurements, the postretirement benefit plans assets measured at fair value as of December 31, 2011:
## Table 1 ##
(a) Medical benefit (health and welfare) component for 401(h) accounts to fund a portion of the postretirement obligation.
These 401(h) assets are included in the pension plan assets shown above.
(b) Payables related to pending security purchases, offset by Medicare, interest receivables, and receivables related to pending security sales.
The following table sets forth, by level within the fair value hierarchy discussed in Note 8 – Fair Value Measurements, the postretirement benefit plans assets measured at fair value as of December 31, 2010:
## Table 2 ##
(a) Medical benefit (health and welfare) component for 401(h) accounts to fund a portion of the postretirement obligation.
These 401(h) assets are included in the pension plan assets shown above.
(b) Payables related to pending security purchases, offset by Medicare, interest receivables, and receivables related to pending security sales
borrowings under the Credit Agreements, commercial paper issuances, and/or, in the case of Ameren Missouri and Ameren Illinois, other short-term affiliate borrowings to support normal operations and temporary capital requirements.
We may reduce our short-term borrowings with cash provided by operations or, at our discretion, with long-term borrowings, or, in the case of Ameren Missouri and Ameren Illinois, with capital contributions from Ameren (parent).
In the near term, our operating cash flows will decrease due to the reduction in the federal statutory income tax rate enacted under the TCJA.
The decrease in operating cash flows results from reduced customer rates, reflecting the tax rate decrease, without a corresponding reduction in income tax payments until about 2020 because of our use of net operating losses and tax credit carryforwards.
Additionally, operating cash flows will be further reduced by lower customer rates, resulting from the return of excess deferred taxes.
Over time, the decrease in operating cash flows will be offset as temporary differences between book and taxable income reverse, and by increased customer rates due to higher rate base amounts resulting from lower accumulated deferred income tax liabilities.
We expect to make significant capital expenditures over the next five years as we invest in our electric and natural gas utility infrastructure to support overall system reliability, grid modernization, renewable energy requirements, environmental compliance, and other improvements.
As part of its plan to fund these cash flow requirements, beginning in the first quarter of 2018, Ameren began using newly issued shares, rather than market-purchased shares, to satisfy requirements under the DRPlus and employee benefit plans and expects to continue to do so through at least 2023.
Ameren also plans to issue incremental common equity to fund a portion of Ameren Missouri’s wind generation investments.
Ameren, Ameren Missouri, and Ameren Illinois expect their respective equity to total capitalization levels over the period ending December 2023 to remain in-line with their respective equity to total capitalization levels as of December 31, 2018.
The use of cash provided by operating activities and short-term borrowings to fund capital expenditures and other longterm investments may periodically result in a working capital deficit, defined as current liabilities exceeding current assets, as was the case at December 31, 2018, for the Ameren Companies.
The working capital deficit as of December 31, 2018, was primarily the result of current maturities of long-term debt and our decision to finance our businesses with lower-cost commercial paper issuances.
With the credit capacity available under the Credit Agreements, along with cash and cash equivalents, Ameren had net available liquidity of $1.5 billion at December 31, 2018.
See Credit Facility Borrowings and Liquidity below for additional information.
The following table presents net cash provided by (used in) operating, investing and financing activities for the years ended December 31, 2018, 2017, and 2016:
## Table 3 ##
Cash Flows from Operating Activities Our cash provided by operating activities is affected by fluctuations of trade accounts receivable, inventories, and accounts and wages payable, among other things, as well as the unique regulatory environment for each of our businesses.
Substantially all expenditures related to fuel, purchased power, and natural gas purchased for resale are recovered from customers through rate adjustment mechanisms, which may be adjusted without a traditional rate proceeding.
Similar regulatory mechanisms exist for certain operating expenses that can also affect the timing of cash provided by operating activities.
The timing of cash payments for costs recoverable under our regulatory mechanisms differs from the recovery period of those costs.
Additionally, the seasonality of our electric and natural gas businesses, primarily caused by changes in customer demand due to weather, significantly affect the amount and timing of our cash provided by operating activities.
See Part 1, Item 1, and Note 1 – Summary of Significant Accounting Policies and Note 2 – Rate and Regulatory Matters under Part II, Item 8, of this report for more information about our rate-adjustment mechanisms.2018 versus 2017 Ameren Ameren’s cash from operating activities increased $52 million in 2018 compared with 2017.
The following items contributed to the increase: ‰ A $220 million increase resulting from electric and natural gas margins, as discussed in Results of Operations, excluding certain noncash items, as well as the change in customer receivable balances.
‰ A $27 million decrease in payments for nuclear refueling and maintenance outages at Ameren Missouri’s Callaway energy center.
There was no refueling and maintenance outage in 2018; however, there were cash expenditures related to the 2019 scheduled outage paid in 2018.
Future impairments would be recorded in income from continuing operations.
The statement provides specific guidance for testing goodwill for impairment.
The Company had $3.2 billion of goodwill at December 31, 2001.
Goodwill amortization was $62 million for the year ended December 31, 2001.
The Company is currently assessing the impact of SFAS No.142 on its financial position and results of operations.
In June 2001, the FASB issued SFAS No.143, ‘‘Accounting for Asset Retirement Obligations,’’ which addresses financial accounting and reporting for obligations associated with the retirement of tangible long-lived assets and the associated asset retirement costs.
This statement is effective for financial statements issued for fiscal years beginning after June 15, 2002.
The statement requires recognition of legal obligations associated with the retirement of a long-lived asset, except for certain obligations of lessees.
The Company is currently assessing the impact of SFAS No.143 on its financial position and results of operations.
In December 2001, the FASB revised its earlier conclusion, Derivatives Implementation Group (‘‘DIG’’) Issue C-15, related to contracts involving the purchase or sale of electricity.
Contracts for the purchase or sale of electricity, both forward and option contracts, including capacity contracts, may qualify for the normal purchases and sales exemption and are not required to be accounted for as derivatives under SFAS No.133.
In order for contracts to qualify for this exemption, they must meet certain criteria, which include the requirement for physical delivery of the electricity to be purchased or sold under the contract only in the normal course of business.
Additionally, contracts that have a price based on an underlying that is not clearly and closely related to the electricity being sold or purchased or that are denominated in a currency that is foreign to the buyer or seller are not considered normal purchases and normal sales and are required to be accounted for as derivatives under SFAS No.133.
This revised conclusion is effective beginning April 1, 2002.
The Company is currently assessing the impact of revised DIG Issue C-15 on its financial condition and results of operations.2001 COMPARED TO 2000 Revenues Revenues increased $1.8 billion, or 24% to $9.3 billion in 2001 from $7.5 billion in 2000.
The increase in revenues is due to the acquisition of new businesses, new operations from greenfield projects and positive improvements from existing operations.
Excluding businesses acquired or that commenced commercial operations in 2001 or 2000, revenues increased 5% to $7.1 billion in 2001.
The following table shows the revenue of each segment:

Tables referenced above, in order (Table 0 first):
<table><tr><td></td><td> Beginning Balanceat January 1,</td><td>Actual Return on Plan Assets Related to Assets Still Held at the Reporting Date</td><td colspan="2"> Actual Return on Plan Assets Related to Assets Sold During thePeriod</td><td>Purchases, Sales,and Settlements, net</td><td colspan="2"> Net Transfers into (out of) of Level 3</td><td> Ending Balance at December 31,</td></tr><tr><td> 2011:</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Real estate</td><td>$98</td><td>$10</td><td> $</td><td> -</td><td>$-</td><td> $</td><td> -</td><td>$108</td></tr><tr><td>Private equity</td><td>28</td><td>-10</td><td> </td><td> 11</td><td>-6</td><td> </td><td> -</td><td>23</td></tr><tr><td> 2010:</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Other debt securities</td><td>$1</td><td>$-</td><td></td><td>$-</td><td>$-1</td><td></td><td>$-</td><td>$-</td></tr><tr><td>Real estate</td><td>90</td><td>7</td><td></td><td>-</td><td>1</td><td></td><td>-</td><td>98</td></tr><tr><td>Private equity</td><td>33</td><td>-5</td><td></td><td>7</td><td>-7</td><td></td><td>-</td><td>28</td></tr></table>
<table><tr><td></td><td> Quoted Prices in Active Markets for Identified Assets (Level1)</td><td> Significant Other Observable Inputs (Level 2)</td><td> Significant Other Unobservable Inputs (Level 3)</td><td>Total</td></tr><tr><td>Cash and cash equivalents</td><td>$1</td><td>$66</td><td>$-</td><td>$67</td></tr><tr><td>Equity securities:</td><td></td><td></td><td></td><td></td></tr><tr><td>U.S. large capitalization</td><td>235</td><td>78</td><td>-</td><td>313</td></tr><tr><td>U.S. small and mid-capitalization</td><td>57</td><td>-</td><td>-</td><td>57</td></tr><tr><td>International</td><td>44</td><td>56</td><td>-</td><td>100</td></tr><tr><td>Debt securities:</td><td></td><td></td><td></td><td></td></tr><tr><td>Corporate bonds</td><td>-</td><td>61</td><td>-</td><td>61</td></tr><tr><td>Municipal bonds</td><td>-</td><td>86</td><td>-</td><td>86</td></tr><tr><td>U.S. treasury and agency securities</td><td>-</td><td>82</td><td>-</td><td>82</td></tr><tr><td>Asset-backed securities</td><td>-</td><td>23</td><td>-</td><td>23</td></tr><tr><td>Other</td><td>-</td><td>49</td><td>-</td><td>49</td></tr><tr><td>Total</td><td>$337</td><td>$501</td><td>$-</td><td>$838</td></tr><tr><td>Plus: Medical benefit assets at December 31<sup>(a)</sup></td><td></td><td></td><td></td><td>91</td></tr><tr><td>Less: Net payables at December31<sup>(b)</sup></td><td></td><td></td><td></td><td>-33</td></tr><tr><td>Fair value of postretirement benefit plans assets at year end</td><td></td><td></td><td></td><td>$896</td></tr></table>
<table><tr><td></td><td> Quoted Prices in Active Markets for Identified Assets (Level1)</td><td> Significant Other Observable Inputs (Level 2)</td><td> Significant Other Unobservable Inputs (Level 3)</td><td>Total</td></tr><tr><td>Cash and cash equivalents</td><td>$-</td><td>$35</td><td>$-</td><td>$35</td></tr><tr><td>Equity securities:</td><td></td><td></td><td></td><td></td></tr><tr><td>U.S. large capitalization</td><td>215</td><td>72</td><td>-</td><td>287</td></tr><tr><td>U.S. small and mid-capitalization</td><td>66</td><td>-</td><td>-</td><td>66</td></tr><tr><td>International</td><td>43</td><td>51</td><td>-</td><td>94</td></tr><tr><td>Debt securities:</td><td></td><td></td><td></td><td></td></tr><tr><td>Corporate bonds</td><td>-</td><td>59</td><td>-</td><td>59</td></tr><tr><td>Municipal bonds</td><td>-</td><td>58</td><td>-</td><td>58</td></tr><tr><td>U.S. treasury and agency securities</td><td>-</td><td>59</td><td>-</td><td>59</td></tr><tr><td>Asset-backed securities</td><td>-</td><td>31</td><td>-</td><td>31</td></tr><tr><td>Other</td><td>-</td><td>29</td><td>-</td><td>29</td></tr><tr><td>Total</td><td>$324</td><td>$394</td><td>$-</td><td>$718</td></tr><tr><td>Plus: Medical benefit assets at December 31<sup>(a)</sup></td><td></td><td></td><td></td><td>85</td></tr><tr><td>Less: Net payables at December31<sup>(b)</sup></td><td></td><td></td><td></td><td>-6</td></tr><tr><td>Fair value of postretirement benefit plans assets at year end</td><td></td><td></td><td></td><td>$797</td></tr></table>
<table><tr><td></td><td colspan="3">Net Cash Provided byOperating Activities</td><td colspan="3">Net Cash Used inInvesting Activities</td><td colspan="3">Net Cash Provided by (Used in)Financing Activities</td></tr><tr><td></td><td>2018</td><td>2017</td><td>2016</td><td>2018</td><td>2017</td><td>2016</td><td>2018</td><td>2017</td><td>2016</td></tr><tr><td>Ameren</td><td>$2,170</td><td>$2,118</td><td>$2,117</td><td>$-2,336</td><td>$-2,204</td><td>$-2,158</td><td>$205</td><td>$102</td><td>$-258</td></tr><tr><td>Ameren Missouri</td><td>1,260</td><td>1,017</td><td>1,169</td><td>-976</td><td>-684</td><td>-937</td><td>-283</td><td>-331</td><td>-434</td></tr><tr><td>Ameren Illinois</td><td>659</td><td>828</td><td>796</td><td>-1,248</td><td>-1,070</td><td>-918</td><td>628</td><td>255</td><td>51</td></tr></table>

Question: Which year is Private equity of Beginning Balanceat January 1 the least?
Answer: 2011