Principal Financial Group, Inc.  Notes to Consolidated Financial Statements — (continued) 1.
Nature of Operations and Significant Accounting Policies — (continued) The effects of reinsurance on premiums and other considerations and policy and contract benefits were as follows:
## Table 0 ##
Separate Accounts The separate account assets presented in the consolidated financial statements represent the fair market value of funds that are separately administered by us for contracts with equity, real estate and fixed income investments.
The separate account contract owner, rather than us, bears the investment risk of these funds.
The separate account assets are legally segregated and are not subject to claims that arise out of any of our other business.
We receive fees for mortality, withdrawal, and expense risks, as well as administrative, maintenance and investment advisory services, that are included in the consolidated statements of operations.
Net deposits, net investment income and realized and unrealized capital gains and losses on the separate accounts are not reflected in the consolidated statements of operations.
At December 31, 2008 and 2007, the separate accounts include a separate account valued at $207.4 million and $748.8 million, respectively, which primarily includes shares of our stock that were allocated and issued to eligible participants of qualified employee benefit plans administered by us as part of the policy credits issued under our 2001 demutualization.
These shares are included in both basic and diluted earnings per share calculations.
In the consolidated statements of financial position, the separate account shares are recorded at fair value and are reported as separate account assets with a corresponding separate account liability to eligible participants of the qualified plan.
Changes in fair value of the separate account shares are reflected in both the separate account assets and separate account liabilities and do not impact our results of operations.
Income Taxes We file a U. S.  consolidated income tax return that includes all of our qualifying subsidiaries.
Our policy of allocating income tax expenses and benefits to companies in the group is generally based upon pro rata contribution of taxable income or operating losses.
We are taxed at U. S.  corporate rates on taxable income based on existing tax laws.
Current income taxes are charged or credited to net income based upon amounts estimated to be payable or recoverable as a result of taxable operations for the current year.
Deferred income taxes are provided for the tax effect of temporary differences in the financial reporting and income tax bases of assets and liabilities and net operating losses using enacted income tax rates and laws.
The effect on deferred income tax assets and deferred income tax liabilities of a change in tax rates is recognized in operations in the period in which the change is enacted.
Foreign Exchange Assets and liabilities of our foreign subsidiaries and affiliates denominated in non-U.
S.  dollars, where the U. S.  dollar is not the functional currency, are translated into U. S.  dollar equivalents at the year-end spot foreign exchange rates.
Resulting translation adjustments are reported as a component of stockholders’ equity, along with any related hedge and tax effects.
Revenues and expenses for these entities are translated at the weighted-average exchange rates for the year.
Revenue, expense and other foreign currency transaction and translation adjustments that affect cash flows are reported in net income, along with related hedge and tax effects.
Goodwill and Other Intangibles Goodwill and other intangibles include the cost of acquired subsidiaries in excess of the fair value of the net tangible assets recorded in connection with acquisitions.
Goodwill and indefinite-lived intangible assets are not amortized.
Rather,
the fair value has been below cost; (2) the reasons for the decline in value; (3) the financial position and access to capital of the issuer, including the current and future impact of any specific events and (4) our ability and intent to hold the security for a period of time that allows for the recovery in value which, in some cases, may extend to maturity.
To the extent we determine that a security is deemed to be other than temporarily impaired, the difference between amortized cost and fair value would be charged to net income.
There are a number of significant risks and uncertainties inherent in the process of monitoring credit impairments and determining if an impairment is other than temporary.
These risks and uncertainties include: (1) the risk that our assessment of an issuer’s ability to meet all of its contractual obligations will change based on changes in the credit characteristics of that issuer, (2) the risk that the economic outlook will be worse than expected or have more of an impact on the issuer than anticipated, (3) the risk that our investment professionals are making decisions based on fraudulent or misstated information in the financial statements provided by issuers and (4) the risk that new information obtained by us or changes in other facts and circumstances lead us to change our intent to hold the security to maturity or until it recovers in value.
Any of these situations could result in a charge to net income in a future period.
The net realized loss relating to other than temporary credit impairments of fixed maturity securities was $397.0 million and $207.3 million for the year ended December 31, 2008 and 2007, respectively.
For the year ended December 31, 2008 and 2007, we realized $16.1 million and $34.6 million of gross realized losses upon disposal of bonds excluding hedging adjustments.
Included in the 2008 loss is $13.7 million related to sales of sixteen names that experienced credit deterioration during the period.
Included in the 2007 loss is $32.3 million related to sales of forty-two credit impaired and credit related names.
We generally intend to hold securities in unrealized loss positions until they mature or recover.
However, we do sell bonds under certain circumstances, such as when we have evidence of a significant deterioration in the issuer’s creditworthiness, when a change in regulatory requirements modifies what constitutes a permissible investment or the maximum level of investments held or when there is an increase in capital requirements or a change in risk weights of debt securities.
Sales generate both gains and losses.
Fixed Maturity Securities Available-for-Sale The following tables present our fixed maturity securities available-for-sale by industry category and the associated gross unrealized gains and losses as of December 31, 2008 and 2007.
## Table 1 ##
(1) Includes exposure to Alt-a mortgage loans with an amortized cost of $67.3 million, gross unrealized losses of $17.3 million and a carrying amount of $50.0 million.
The Alt-a portfolio has a weighted average rating of AA and 66% are 2005 and prior vintages.
The pension plan investments are held in a Master Trust, with The Northern Trust Company.
Investments in the Master Trust are valued at fair value, which has been determined based on fair value of the underlying investments of the Master Trust.
Investments in securities traded on public security exchanges are valued at their closing market prices on the valuation date; where no sale was made on the valuation date, the security is generally valued at its most recent bid price.
Certain short-term investments are carried at cost, which approximates fair value.
Investments in registered investment companies and common trust funds, which primarily invest in stocks, bonds, and commodity futures, are valued using publicly available market prices for the underlying investments held by these entities.
The majority of pension plan assets are invested in equity securities, because equity portfolios have historically provided higher returns than debt and other asset classes over extended time horizons, and are expected to do so in the future.
Correspondingly, equity investments also entail greater risks than other investments.
Equity risks are balanced by investing a significant portion of the plan’s assets in high quality debt securities.
The average quality rating of the debt portfolio exceeded AA as of December 31, 2008 and 2007.
The debt portfolio is also broadly diversified and invested primarily in U. S.  Treasury, mortgage, and corporate securities with an intermediate average maturity.
The weighted-average maturity of the debt portfolio was 5 years at both December 31, 2008 and 2007, respectively.
The investment of pension plan assets in securities issued by Union Pacific is specifically prohibited for both the equity and debt portfolios, other than through index fund holdings.
Other Retirement Programs Thrift Plan – We provide a defined contribution plan (thrift plan) to eligible non-union employees and make matching contributions to the thrift plan.
We match 50 cents for each dollar contributed by employees up to the first six percent of compensation contributed.
Our thrift plan contributions were $14 million in 2008, $14 million in 2007, and $13 million in 2006.
Railroad Retirement System – All Railroad employees are covered by the Railroad Retirement System (the System).
Contributions made to the System are expensed as incurred and amounted to approximately $620 million in 2008, $616 million in 2007, and $615 million in 2006.
Collective Bargaining Agreements – Under collective bargaining agreements, we provide certain postretirement healthcare and life insurance benefits for eligible union employees.
Premiums under the plans are expensed as incurred and amounted to $49 million in 2008 and $40 million in both 2007 and 2006.5.
Other Income Other income included the following for the years ended December 31:
## Table 2 ##

<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">(in millions)</td></tr><tr><td>Premiums and other considerations:</td><td></td><td></td><td></td></tr><tr><td>Direct</td><td>$4,495.1</td><td>$4,751.3</td><td>$4,468.8</td></tr><tr><td>Assumed</td><td>9.7</td><td>160.0</td><td>117.3</td></tr><tr><td>Ceded</td><td>-295.6</td><td>-277.2</td><td>-280.8</td></tr><tr><td>Net premiums and other considerations</td><td>$4,209.2</td><td>$4,634.1</td><td>$4,305.3</td></tr><tr><td>Benefits, claims and settlement expenses:</td><td></td><td></td><td></td></tr><tr><td>Direct</td><td>$6,440.8</td><td>$6,489.7</td><td>$5,871.3</td></tr><tr><td>Assumed</td><td>43.5</td><td>190.4</td><td>141.8</td></tr><tr><td>Ceded</td><td>-264.4</td><td>-244.8</td><td>-320.7</td></tr><tr><td>Net benefits, claims and settlement expenses</td><td>$6,219.9</td><td>$6,435.3</td><td>$5,692.4</td></tr></table>
<table><tr><td> </td><td colspan="4"> December 31, 2008</td></tr><tr><td> </td><td> Amortized cost</td><td> Gross unrealized gains</td><td> Gross unrealized losses</td><td> Carrying amount</td></tr><tr><td> </td><td colspan="4"><i>(in millions)</i> </td></tr><tr><td>Finance — Banking</td><td>$4,248.7</td><td>$14.9</td><td>$1,095.1</td><td>$3,168.5</td></tr><tr><td>Finance — Brokerage</td><td>785.4</td><td>0.9</td><td>128.5</td><td>657.8</td></tr><tr><td>Finance — Finance Companies</td><td>418.6</td><td>0.1</td><td>84.7</td><td>334.0</td></tr><tr><td>Finance — Financial Other</td><td>753.3</td><td>6.8</td><td>104.6</td><td>655.5</td></tr><tr><td>Finance — Insurance</td><td>2,885.8</td><td>38.1</td><td>706.6</td><td>2,217.3</td></tr><tr><td>Finance — REITS</td><td>1,412.5</td><td>—</td><td>430.6</td><td>981.9</td></tr><tr><td>Industrial — Basic Industry</td><td>2,030.0</td><td>10.6</td><td>303.8</td><td>1,736.8</td></tr><tr><td>Industrial — Capital Goods</td><td>2,322.3</td><td>15.1</td><td>316.8</td><td>2,020.6</td></tr><tr><td>Industrial — Communications</td><td>2,943.7</td><td>32.3</td><td>297.0</td><td>2,679.0</td></tr><tr><td>Industrial — Consumer Cyclical</td><td>2,023.8</td><td>18.7</td><td>338.7</td><td>1,703.8</td></tr><tr><td>Industrial — Consumer Non-Cyclical</td><td>3,184.7</td><td>31.2</td><td>298.5</td><td>2,917.4</td></tr><tr><td>Industrial — Energy</td><td>1,958.0</td><td>9.6</td><td>224.5</td><td>1,743.1</td></tr><tr><td>Industrial — Other</td><td>952.8</td><td>2.4</td><td>117.6</td><td>837.6</td></tr><tr><td>Industrial — Technology</td><td>876.7</td><td>2.2</td><td>115.3</td><td>763.6</td></tr><tr><td>Industrial — Transportation</td><td>992.2</td><td>10.3</td><td>124.5</td><td>878.0</td></tr><tr><td>Utility — Electric</td><td>2,473.4</td><td>22.8</td><td>199.2</td><td>2,297.0</td></tr><tr><td>Utility — Natural Gas</td><td>1,142.0</td><td>4.9</td><td>110.7</td><td>1,036.2</td></tr><tr><td>Utility — Other</td><td>156.7</td><td>2.3</td><td>14.3</td><td>144.7</td></tr><tr><td>Government guaranteed</td><td>799.5</td><td>75.0</td><td>57.0</td><td>817.5</td></tr><tr><td>Total corporate securities</td><td>32,360.1</td><td>298.2</td><td>5,068.0</td><td>27,590.3</td></tr><tr><td>Residential pass-through securities</td><td>1,627.5</td><td>50.5</td><td>0.5</td><td>1,677.5</td></tr><tr><td>Commercial mortgage-backed securities</td><td>5,682.7</td><td>3.7</td><td>2,081.9</td><td>3,604.5</td></tr><tr><td>Residential collateralized mortgage obligations -1</td><td>950.8</td><td>6.4</td><td>188.6</td><td>768.6</td></tr><tr><td>Asset-backed securities — Home equity -2</td><td>545.1</td><td>0.1</td><td>198.5</td><td>346.7</td></tr><tr><td>Asset-backed securities — All other</td><td>816.1</td><td>16.8</td><td>137.2</td><td>695.7</td></tr><tr><td>Collateralized debt obligations — Credit</td><td>202.8</td><td>—</td><td>123.6</td><td>79.2</td></tr><tr><td>Collateralized debt obligations — CMBS</td><td>302.2</td><td>—</td><td>173.3</td><td>128.9</td></tr><tr><td>Collateralized debt obligations — Loans</td><td>91.4</td><td>—</td><td>54.4</td><td>37.0</td></tr><tr><td>Collateralized debt obligations — ABS -3</td><td>100.0</td><td>0.2</td><td>53.5</td><td>46.7</td></tr><tr><td>Total mortgage-backed and other asset-backed securities</td><td>10,318.6</td><td>77.7</td><td>3,011.5</td><td>7,384.8</td></tr><tr><td>U.S. Government and agencies</td><td>548.4</td><td>46.9</td><td>0.1</td><td>595.2</td></tr><tr><td>States and political subdivisions</td><td>2,113.8</td><td>32.6</td><td>120.9</td><td>2,025.5</td></tr><tr><td>Non-U.S. governments</td><td>462.1</td><td>31.5</td><td>15.1</td><td>478.5</td></tr><tr><td>Total fixed maturity securities, available-for-sale</td><td>$45,803.0</td><td>$486.9</td><td>$8,215.6</td><td>$38,074.3</td></tr></table>
<table><tr><td><i>Millions of Dollars</i></td><td>2008</td><td>2007</td><td>2006</td></tr><tr><td>Rental income</td><td>$87</td><td>$68</td><td>$83</td></tr><tr><td>Net gain on non-operating asset dispositions</td><td>41</td><td>52</td><td>72</td></tr><tr><td>Interest income</td><td>21</td><td>50</td><td>29</td></tr><tr><td>Sale of receivables fees</td><td>-23</td><td>-35</td><td>-33</td></tr><tr><td>Non-operating environmental costs and other</td><td>-34</td><td>-19</td><td>-33</td></tr><tr><td>Total</td><td>$92</td><td>$116</td><td>$118</td></tr></table>

Question: what was the percentage change in rental income from 2006 to 2007?
Answer: -0.18072