Principal Financial Group, Inc.  Notes to Consolidated Financial Statements — (continued) 12.
Debt Short-Term Debt The components of short-term debt as of December 31, 2008 and 2007, were as follows:
## Table 0 ##
As of December 31, 2008, we had credit facilities with various financial institutions in an aggregate amount of $792.4 million.
As of December 31, 2008 and 2007, we had $500.9 million and $290.8 million of outstanding borrowings related to our credit facilities, with zero and $30.3 million of assets pledged as support, respectively.
Assets pledged consisted primarily of commercial mortgages and securities.
Our credit facilities include a $600.0 million commercial paper program, of which we issued $482.3 million as of December 31, 2008, $233.0 million of which was issued under the Federal Reserve’s Commercial Paper Funding Facility.
Our commercial paper program has a back-stop facility to provide 100% support for our commercial paper program, of which there were no outstanding balances as of December 31, 2008.
On October 5, 2008, Lehman Commercial Paper Inc.  (‘‘LCP’’), a subsidiary of Lehman Brothers Holdings Inc. , filed for protection under Chapter 11 of the Federal Bankruptcy Code in the U. S.  Bankruptcy Court for the Southern District of New York.
LCP is a lender under our credit facilities and had committed to provide $21.0 million under each facility.
We are uncertain whether LCP will fulfill its commitments under the credit facilities in light of its bankruptcy filing.
The weighted-average interest rates on short-term borrowings as of December 31, 2008 and 2007, were 2.7% and 5.1% respectively.
Long-Term Debt The components of long-term debt as of December 31, 2008 and 2007, were as follows:
## Table 1 ##
The amounts included above are net of the discount and premium associated with issuing these notes, which are being amortized to expense over their respective terms using the interest method.
On October 16 and December 5, 2006, we issued $500.0 million and $100.0 million, respectively, of senior notes.
The notes bear interest at a rate of 6.05% per year.
Interest on the notes is payable semi-annually on April 15 and October 15 each year and began on April 15, 2007.
The notes will mature on October 15, 2036.
A portion of the proceeds were used to fund the acquisition of WM Advisors, Inc. , with the remaining proceeds being used for general corporate purposes.
On November 3, 2005, Principal International de Chile S. A. , a wholly owned indirect subsidiary, entered into long-term borrowing agreements with two Chilean banks in the amount of US $93.9 million.
This debt is denominated in Unidades de Formento (‘‘UF’’), a Chilean inflation-indexed, peso-denominated monetary unit.
Of this amount, US $49.0 million of UF +3.31% notes, which was refinanced from +4.59% during 2007, and US $44.9 million of UF +3.63% notes, which was refinanced from +4.93% in 2007, mature on November 3, 2011.
In November 2007, we paid down US $17.7 million on the UF +3.63% notes.
Interest on the notes is payable semi-annually on May 3 and November 3 each year.
The debt outstanding and interest expense will vary due to fluctuations in the Chilean peso to US dollar exchange rates and Chilean inflation.
On August 25, 1999, Principal Financial Group (Australia) Holdings Pty.
Limited, a wholly owned indirect subsidiary, issued $665.0 million of unsecured redeemable long-term debt.
Of this amount, $200.0 million of 7.95% notes matured on August 15, 2004, with the remaining $465.0 million in 8.2% notes due August 15, 2009.
In August 2007, we
Principal Financial Group, Inc.  Notes to Consolidated Financial Statements — (continued) 12.
Debt — (continued) repurchased $10.0 million of the remaining notes, leaving $455.0 million in 8.2% notes due on August 15, 2009.
Interest on the notes is payable semiannually on February 15 and August 15 of each year.
Principal Financial Group (Australia) Holdings Pty.
Limited used the net proceeds from the notes to partially fund the purchase of the outstanding stock of several companies affiliated with Bankers Trust Australia Group.
On December 28, 2001, all of the long-term debt obligations of Principal Financial Group (Australia) Holdings Pty.
Limited were assumed by its parent, Principal Financial Services, Inc.  On March 10, 1994, Principal Life issued $100.0 million of surplus notes due March 1, 2044, at an 8% annual interest rate.
None of our affiliates hold any portion of the notes.
Each payment of interest and principal on the notes, however, may be made only with the prior approval of the Commissioner of Insurance of the State of Iowa (the ‘‘Commissioner’’) and only to the extent that Principal Life has sufficient surplus earnings to make such payments.
Interest of $8.0 million for each of the years ended December 31, 2008, 2007 and 2006 was approved by the Commissioner, and charged to expense.
Subject to Commissioner approval, the notes due March 1, 2044, may be redeemed at Principal Life’s election on or after March 1, 2014, in whole or in part at a redemption price of approximately 102.3% of par.
The approximate 2.3% premium is scheduled to gradually diminish over the following ten years.
These notes may be redeemed on or after March 1, 2024, at a redemption price of 100% of the principal amount plus interest accrued to the date of redemption.
The non-recourse mortgages, other mortgages and notes payable are primarily financings for real estate developments.
Outstanding principal balances as of December 31, 2008, ranged from $6.0 million to $9.3 million per development with interest rates generally ranging from 5.5% to 5.8%.
Outstanding principal balances as of December 31, 2007, ranged from $3.0 million to $41.2 million per development with interest rates generally ranging from 5.5% to 8.1%.
Outstanding debt is secured by the underlying real estate properties, which were reported as real estate on our consolidated statements of financial position with a carrying value of $30.4 million and $141.1 million as of December 31, 2008 and 2007, respectively.
Also included in non-recourse mortgages and notes payable is a long-term debt obligation we assumed with the purchase of WM Advisors, Inc.  As part of the purchase, we are bound by a class B share financing agreement previously entered into by WM Advisors, Inc.  and a third party, which was assigned a value of $86.9 million at purchase.
Load mutual fund shares sold without a front end load are referred to as ‘‘B shares’’.
In exchange for paying the selling commission, we receive fees in the future to recover the up-front commission cost incurred.
Prior to our purchase, WM Advisors, Inc.  had entered into a purchase and sale agreement whereby the third party would purchase the rights to future cash flow streams in exchange for funding the sales commissions.
The fair value of these relinquished fees is reported as a long-term debt liability.
There will be no additional sales under this agreement following the effective date of the purchase.
Therefore, this liability will be extinguished within six years, which equates to the contractual term in which the fund can recover fees to cover the upfront commission costs.
The value of this obligation as of December 31, 2008 and 2007, was $36.8 million and $66.6 million, respectively.
At December 31, 2008, future annual maturities of the long-term debt were as follows (in millions):
## Table 2 ##
13.
Income Taxes Our income tax expense (benefit) from continuing operations was as follows:
## Table 3 ##
Principal Financial Group, Inc.  Notes to Consolidated Financial Statements 21.
Earnings Per Common Share The computations of the basic and diluted per share amounts for our continuing operations were as follows:
## Table 4 ##
The calculation of diluted earnings per share for the years ended December 31, 2008, 2007 and 2006, excludes the incremental effect related to certain outstanding stock-based compensation grants due to their anti-dilutive effect.22.
Quarterly Results of Operations (Unaudited) The following is a summary of unaudited quarterly results of operations for 2008 and 2007:
## Table 5 ##
Net cash used in investing activities was $2,917.2 million, $4,499.2 million and $3,910.4 million for the years ended December 31, 2008, 2007 and 2006, respectively.
The decrease in cash used in investing activities was primarily the result of a decrease in net purchases of investments as we have held and are holding higher cash balances to cover potential near term obligations and to further reposition our investment portfolio as necessary.
The increase in cash used in investing activities in 2007 compared to 2006 was primarily due to an increase in net purchases of mortgage loans, available-for-sale securities and real estate as well as additional contributions in 2007 to an equity method investment with no corresponding activity in 2006.
This increase was partially offset by larger acquisitions in 2006 relative to 2007.
Net cash provided by financing activities was $1,956.0 million, $1,292.1 million and $1,586.5 million for the years ended December 31, 2008, 2007 and 2006, respectively.
The increase in cash provided by financing activities in 2008 compared to 2007 is primarily due to our actions to increase liquidity and manage capital risk via a reduction in the acquisition of treasury stock as well as the reduction of our common stock dividend from prior year levels.
The decrease in cash provided by financing activities in 2007 compared to 2006 was primarily due to the issuance of $600.0 million of senior notes from our shelf registration in 2006, with no corresponding activity in 2007 as well as a decrease in net deposits of investment contracts, offset in part by proceeds from short-term debt in the current year, compared to payments of short-term debt in the previous year.
We will have $454.9 million of long-term debt due in 2009; our plan is to refinance this debt.
We have applied to participate in the FDIC Temporary Liquidity Guarantee Program (‘‘TLGP’’) program.
If we do not qualify for the FDIC TLGP, we may not be able to issue debt into the capital markets on terms that are favorable to us or at all due to, among other things, the continuing disruptions in the financial markets and/or investor preference for debt issued by participants in the TLGP.
If the public debt markets are not accessible to us, we believe that we have several options to refinance this debt, including: use of our commercial paper program, reduction of our common dividend, or a dividend of excess liquidity from Principal Life, funded by either cash or selling cash equivalents.
In the event that no debt sources are available to refinance the $454.9 million of long-term debt, we may have to recognize a gain or loss on certain interest rate hedges.
For more information regarding the derivatives, see Item 8.
‘‘Financial Statements and Supplementary Data, Notes to Consolidated Financial Statements, Note 8, Derivative Financial Instruments’’ under the caption, ‘‘Cash Flow Hedges.
’’ Shelf Registration.
We currently have an effective shelf registration which allows us the ability to issue, in unlimited amounts, unsecured senior debt securities or subordinated debt securities, junior subordinated debt, preferred stock, common stock, warrants, depository shares, stock purchase contracts and stock purchase units of PFG, trust preferred securities of three subsidiary trusts and guarantees by PFG of these trust preferred securities.
Our wholly owned subsidiary, PFS, may guarantee, fully and unconditionally or otherwise, our obligations with respect to any non-convertible securities, other than common stock, described in the shelf registration.
For information on senior notes issued from our shelf registration, see Item 8.
‘‘Financial Statements and Supplementary Data, Notes to Consolidated Financial Statements, Note 12, Debt.
’’ Short-Term Debt and Long-Term Debt.
For debt information, see Item 8.
‘‘Financial Statements and Supplementary Data, Notes to Consolidated Financial Statements, Note 12, Debt.
’’ Stockholders’ Equity.
Proceeds from the issuance of our common stock were $36.4 million, $73.6 million and $66.2 million in 2008, 2007 and 2006, respectively.
The following table summarizes our return of capital to common stockholders in 2008, 2007 and 2006.
## Table 6 ##
To enhance our liquidity and capital position in the current market, our Board of Directors decided to suspend repurchases of our common stock under our stock repurchase program and reduce our common stock dividend from prior year levels.
The resumption of our stock repurchase program and the declaration and payment of future dividends to the holders of our common stock will be at the discretion of our Board of Directors and will depend on many factors including dividends from our operating subsidiaries, our financial condition and net income, the capital requirements of our subsidiaries, legal requirements, regulatory constraints, our credit and financial strength ratings and such other factors as the Board of Directors deems relevant.
For additional stockholders’ equity information, see Item 8.
‘‘Financial Statements and Supplementary Data, Notes to Consolidated Financial Statements, Note 16, Stockholders’ Equity.
’’
REPUBLIC SERVICES, INC.  NOTES TO CONSOLIDATED FINANCIAL STATEMENTS—(Continued) 11.
EMPLOYEE BENEFIT PLANS Stock-Based Compensation In February 2007, our board of directors approved the 2007 Stock Incentive Plan (2007 Plan), and in May 2007 our shareholders ratified the 2007 Plan.
In March 2011, our board of directors approved the Amended and Restated 2007 Stock Incentive Plan, and in May 2011 our shareholders ratified the Amended and Restated 2007 Stock Incentive Plan.
In March 2013, our board of directors approved the Republic Services, Inc.
Amended and Restated 2007 Stock Incentive Plan (the Amended and Restated Plan), and in May 2013 our shareholders ratified the Amended and Restated Plan.
We currently have approximately 15.6 million shares of common stock reserved for future grants under the Amended and Restated Plan.
Options granted under the 2007 Plan and the Amended and Restated Plan are non-qualified and are granted at a price equal to the fair market value of our common stock at the date of grant.
Generally, options granted have a term of seven to ten years from the date of grant, and vest in increments of 25% per year over a period of four years beginning on the first anniversary date of the grant.
Options granted to non-employee directors have a term of ten years and are fully vested at the grant date.
In December 2008, the board of directors amended and restated the Republic Services, Inc.  2006 Incentive Stock Plan (formerly known as the Allied Waste Industries, Inc.  2006 Incentive Stock Plan) (the 2006 Plan).
Allied’s shareholders approved the 2006 Plan in May 2006.
The 2006 Plan was amended and restated in December 2008 to reflect Republic as the new sponsor of the Plan, to reflect that any references to shares of common stock are to shares of common stock of Republic, and to adjust outstanding awards and the number of shares available under the Plan to reflect the Allied acquisition.
The 2006 Plan, as amended and restated, provided for the grant of nonqualified stock options, incentive stock options, shares of restricted stock, shares of phantom stock, stock bonuses, restricted stock units, stock appreciation rights, performance awards, dividend equivalents, cash awards, or other stock-based awards.
Awards granted under the 2006 Plan prior to December 5, 2008 became fully vested and nonforfeitable upon the closing of the Allied acquisition.
No further awards will be made under the 2006 Plan.
Stock Options We use a lattice binomial option-pricing model to value our stock option grants.
We recognize compensation expense on a straight-line basis over the requisite service period for each separately vesting portion of the award, or to the employee’s retirement eligible date, if earlier.
Expected volatility is based on the weighted average of the most recent one year volatility and a historical rolling average volatility of our stock over the expected life of the option.
The risk-free interest rate is based on Federal Reserve rates in effect for bonds with maturity dates equal to the expected term of the option.
We use historical data to estimate future option exercises, forfeitures (at 3.0% for 2014 and 2013) and expected life of the options.
When appropriate, separate groups of employees that have similar historical exercise behavior are considered separately for valuation purposes.
We did not grant stock options during the year ended December 31, 2015.
The weighted-average estimated fair values of stock options granted during the years ended December 31, 2014 and 2013 were $5.74 and $5.27 per option, respectively, which were calculated using the following weighted-average assumptions:

<table><tr><td> </td><td colspan="2"> December 31,</td></tr><tr><td> </td><td> 2008</td><td> 2007</td></tr><tr><td> </td><td colspan="2"><i>(in millions)</i> </td></tr><tr><td>Commercial paper</td><td>$482.3</td><td>$233.3</td></tr><tr><td>Other recourse short-term debt</td><td>18.6</td><td>57.5</td></tr><tr><td>Total short-term debt</td><td>$500.9</td><td>$290.8</td></tr></table>
<table><tr><td> </td><td colspan="2"> December 31,</td></tr><tr><td> </td><td> 2008</td><td> 2007</td></tr><tr><td> </td><td colspan="2"><i>(in millions)</i> </td></tr><tr><td>8.2% notes payable, due 2009</td><td>$454.9</td><td>$454.7</td></tr><tr><td>3.31% notes payable, due 2011</td><td>49.9</td><td>58.4</td></tr><tr><td>3.63% notes payable, due 2011</td><td>25.6</td><td>29.9</td></tr><tr><td>6.05% notes payable, due 2036</td><td>601.8</td><td>601.9</td></tr><tr><td>8% surplus notes payable, due 2044</td><td>99.2</td><td>99.2</td></tr><tr><td>Non-recourse mortgages and notes payable</td><td>58.7</td><td>129.8</td></tr><tr><td>Other mortgages and notes payable</td><td>0.4</td><td>24.9</td></tr><tr><td>Total long-term debt</td><td>$1,290.5</td><td>$1,398.8</td></tr></table>
<table><tr><td>2009</td><td>$466.5</td></tr><tr><td>2010</td><td>9.5</td></tr><tr><td>2011</td><td>83.0</td></tr><tr><td>2012</td><td>5.6</td></tr><tr><td>2013</td><td>11.9</td></tr><tr><td>Thereafter</td><td>714.0</td></tr><tr><td>Total future maturities of the long-term debt</td><td>$1,290.5</td></tr></table>
<table><tr><td> </td><td colspan="3"> For the year ended December 31,</td></tr><tr><td> </td><td>2008</td><td>2007</td><td> 2006</td></tr><tr><td> </td><td colspan="3"><i>(in millions)</i> </td></tr><tr><td>Current income taxes:</td><td></td><td></td><td></td></tr><tr><td>U.S. federal</td><td>$118.9</td><td>$214.6</td><td>$211.8</td></tr><tr><td>State and foreign</td><td>-4.0</td><td>64.3</td><td>52.8</td></tr><tr><td>Total current income taxes</td><td>114.9</td><td>278.9</td><td>264.6</td></tr><tr><td>Deferred income taxes</td><td>-119.4</td><td>-70.8</td><td>31.3</td></tr><tr><td>Total income taxes (benefits)</td><td>$-4.5</td><td>$208.1</td><td>$295.9</td></tr></table>
<table><tr><td> </td><td colspan="3"> For the year ended December 31,</td></tr><tr><td> </td><td> 2008</td><td> 2007</td><td> 2006</td></tr><tr><td> </td><td colspan="3"><i>(in millions, except per share data)</i> </td></tr><tr><td>Income from continuing operations, net of related income taxes</td><td>$458.1</td><td>$840.1</td><td>$1,035.4</td></tr><tr><td>Subtract:</td><td></td><td></td><td></td></tr><tr><td>Preferred stock dividends</td><td>33.0</td><td>33.0</td><td>33.0</td></tr><tr><td>Income from continuing operations available to common stockholders, net of related income taxes</td><td>$425.1</td><td>$807.1</td><td>$1,002.4</td></tr><tr><td>Weighted-average shares outstanding:</td><td></td><td></td><td></td></tr><tr><td>Basic</td><td>259.3</td><td>265.4</td><td>272.9</td></tr><tr><td>Dilutive effects:</td><td></td><td></td><td></td></tr><tr><td>Stock options</td><td>1.1</td><td>2.3</td><td>2.0</td></tr><tr><td>Performance share awards</td><td>0.4</td><td>—</td><td>—</td></tr><tr><td>Restricted stock units</td><td>0.3</td><td>0.4</td><td>0.6</td></tr><tr><td>Diluted</td><td>261.1</td><td>268.1</td><td>275.5</td></tr><tr><td>Income from continuing operations per common share:</td><td></td><td></td><td></td></tr><tr><td>Basic</td><td>$1.64</td><td>$3.04</td><td>$3.67</td></tr><tr><td>Diluted</td><td>$1.63</td><td>$3.01</td><td>$3.64</td></tr></table>
<table><tr><td> </td><td colspan="4"> For the three months ended</td></tr><tr><td> </td><td>December 31</td><td>September 30</td><td>June 30</td><td> March 31</td></tr><tr><td> </td><td colspan="4"><i>(in millions, except per share data)</i> </td></tr><tr><td> 2008</td><td></td><td></td><td></td><td></td></tr><tr><td>Total revenues</td><td>$2,279.2</td><td>$2,497.8</td><td>$2,658.2</td><td>$2,500.7</td></tr><tr><td>Total expenses</td><td>2,339.7</td><td>2,401.7</td><td>2,452.2</td><td>2,288.7</td></tr><tr><td>Income from continuing operations, net of related income taxes</td><td>0.8</td><td>98.3</td><td>176.6</td><td>182.4</td></tr><tr><td>Preferred stock dividends</td><td>8.3</td><td>8.2</td><td>8.3</td><td>8.2</td></tr><tr><td>Net income (loss) available to common stockholders</td><td>-7.5</td><td>90.1</td><td>168.3</td><td>174.2</td></tr><tr><td>Basic earnings (loss) per common share for income from continuing operations, net of related income taxes</td><td>-0.03</td><td>0.35</td><td>0.65</td><td>0.67</td></tr><tr><td>Basic earnings (loss) per common share for net income available to common stockholders</td><td>-0.03</td><td>0.35</td><td>0.65</td><td>0.67</td></tr><tr><td>Diluted earnings (loss) per common share for income from continuing operations, net of related income taxes</td><td>-0.03</td><td>0.35</td><td>0.64</td><td>0.67</td></tr><tr><td>Diluted earnings (loss) per common share for net income available to common stockholders</td><td>-0.03</td><td>0.35</td><td>0.64</td><td>0.67</td></tr><tr><td> 2007</td><td></td><td></td><td></td><td></td></tr><tr><td>Total revenues</td><td>$2,564.1</td><td>$2,849.6</td><td>$2,831.8</td><td>$2,661.0</td></tr><tr><td>Total expenses</td><td>2,594.5</td><td>2,518.0</td><td>2,419.1</td><td>2,326.7</td></tr><tr><td>Income from continuing operations, net of related income taxes</td><td>21.8</td><td>240.7</td><td>312.3</td><td>265.3</td></tr><tr><td>Income (loss) from discontinued operations, net of related income taxes</td><td>20.6</td><td>-0.2</td><td>-0.2</td><td>—</td></tr><tr><td>Preferred stock dividends</td><td>8.3</td><td>8.2</td><td>8.3</td><td>8.2</td></tr><tr><td>Net income available to common stockholders</td><td>34.1</td><td>232.3</td><td>303.8</td><td>257.1</td></tr><tr><td>Basic earnings per common share for income from continuing operations, net of related income taxes</td><td>0.05</td><td>0.88</td><td>1.14</td><td>0.96</td></tr><tr><td>Basic earnings per common share for net income available to common stockholders</td><td>0.13</td><td>0.88</td><td>1.14</td><td>0.96</td></tr><tr><td>Diluted earnings per share for income from continuing operations, net of related income taxes</td><td>0.05</td><td>0.87</td><td>1.12</td><td>0.95</td></tr><tr><td>Diluted earnings per common share for net income available to common stockholders</td><td>0.13</td><td>0.87</td><td>1.12</td><td>0.95</td></tr></table>
<table><tr><td> </td><td colspan="3"> For the year ended December 31,</td></tr><tr><td> </td><td> 2008</td><td> 2007</td><td> 2006</td></tr><tr><td> </td><td colspan="3"><i>(in millions)</i> </td></tr><tr><td>Dividends to stockholders</td><td>$116.7</td><td>$235.6</td><td>$214.7</td></tr><tr><td>Repurchase of common stock</td><td>6.4</td><td>756.3</td><td>755.8</td></tr><tr><td>Total cash returned to stockholders</td><td>$123.1</td><td>$991.9</td><td>$970.5</td></tr><tr><td>Number of shares repurchased</td><td>1.0</td><td>11.5</td><td>14.5</td></tr></table>

Question: Which year is Income from continuing operations, net of related income taxes the highest?
Answer: 2006