reported U. S.  high-grade TRACE volumes to the adjusted U. S.  high-grade TRACE volumes in the “Investor Relations” section of our website.
Other credit volumes increased by 27.5% for the year ended December 31, 2014 compared to the year ended December 31, 2013, primarily due to increase in estimated market share in emerging markets bonds, Eurobonds and high-yield bonds.
Liquid products volume decreased by 14.1% for the year ended December 31, 2014 compared to the year ended December 31, 2013, due mainly to lower trading volumes in U. S.  agency bonds.
Estimated U. S.  Agency TRACE volumes declined by 17.6% for the year ended December 31, 2014 compared to the year ended December 31, 2013.
Our average variable transaction fee per million for the years ended December 31, 2014 and 2013 was as follows:
## Table 0 ##
The U. S.  high-grade average variable transaction fee per million decreased to $175 per million for the year ended December 31, 2014 from $190 per million for the year ended December 31, 2013.
The change was primarily due to a decrease in the duration, and an increase in the nominal size, of bonds traded.
U. S.  high-grade floating rate average variable transaction fee per million increased from $25 for the year ended December 31, 2013 to $51 for the year ended December 31, 2014, primarily due to a change in our pricing calculation to conform to the market convention for such instruments.
Distribution Fees Distribution fees increased by $3.5 million or 5.8% to $64.9 million for the year ended December 31, 2014 from $61.4 million for the year ended December 31, 2013.
U. S.  high-grade distribution fees increased $4.5 million principally due to the migration over the past year of certain of our broker-dealer clients from an all-variable fee plan to a plan that incorporates a monthly distribution fee.
The $1.4 million decrease in Other credit distribution fees principally relates to the migration of certain Eurobond dealers to plans that incorporate a higher level of variable fees and lower level of monthly distribution fees.
The $0.5 million increase in Liquid products distribution fees was due to the commencement of SEF-related revenues during 2014.
Information and Post-Trade Services.
Information and post-trade services revenues increased by $6.1 million or 24.2% to $31.5 million for the year ended December 31, 2014 from $25.4 million for the year ended December 31, 2013, principally due to the inclusion of two additional months of revenues from Xtrakter in 2014 and the favorable impact of a change in foreign currency exchange rates of $1.3 million.
Xtrakter’s transaction reporting business processed approximately 1,100 million and 943 million transactions for the years ended December 31, 2014 and 2013, respectively.
Technology Products and Services.
Technology products and services revenues increased by $0.5 million or 8.6% to $6.9 million for the year ended December 31, 2014 from $6.3 million for the year ended December 31, 2013.
The increase was primarily a result of higher professional consulting services revenues.
Investment Income.
Investment income increased by $0.1 million or 29.3% to $0.5 million for the year ended December 31, 2014 from $0.4 million for the year ended December 31, 2013, primarily due to a higher average investment balance in 2014.
Other.
Other revenues decreased by $0.2 million or 8.3% to $2.7 million for the year ended December 31, 2014 from $3.0 million for the year ended December 31, 2013.
In the year ended December 31, 2014, we recognized income of $0.9 million on the sale of certain MF Global bankruptcy claims.
In the year ended December 31, 2013, we recorded a gain of $0.8 million on the sale of U. S.  treasuries.
We used the proceeds from the sale of U. S.  treasuries to fund the acquisition of Xtrakter.
MARKETAXESS HOLDINGS INC.  NOTES TO CONSOLIDATED FINANCIAL STATEMENTS – (Continued) Stock Options The exercise price of each option granted is equal to the market price of the Company’s common stock on the date of grant.
Generally, option grants have provided for vesting over a three or five-year period.
Options expire in ten years from the date of grant.
The fair value of each option award is estimated on the date of grant using the Black-Scholes option-pricing model.
The determination of fair value of share-based payment awards on the date of grant using an option-pricing model is affected by the Company’s stock price as well as assumptions regarding a number of highly complex and subjective variables, including the expected stock price volatility over the term of the awards, the risk-free interest rate, the expected dividend yield rate and the expected term.
Expected volatilities are based on historical volatility of the Company’s stock.
The risk-free interest rate is based on U. S.  Treasury securities with a maturity value approximating the expected term of the option.
The dividend yield rate is based on the expected annual dividends to be paid divided by the expected stock price.
The expected term represents the period of time that options granted are expected to be outstanding based on actual and projected employee stock option exercise behavior.
The weighted-average fair value for options granted during 2014, 2013 and 2012 was $19.25, $19.61 and $12.26, respectively.
The following table represents the assumptions used for the Black-Scholes option-pricing model to determine the per share weighted-average fair value for options granted for the three years ended December 31, 2014:
## Table 1 ##
The following table reports stock option activity during the three years ended December 31, 2014 and the intrinsic value as of December 31, 2014:
## Table 2 ##
The intrinsic value is the amount by which the closing price of the Company’s common stock on December 31, 2014 of $71.71 or the price on the day of exercise exceeds the exercise price of the stock options multiplied by the number of shares.
As of December 31, 2014, there was $0.4 million of total unrecognized compensation cost related to non-vested stock options.
That cost is expected to be recognized over a weighted-average period of 1.0 years.
Restricted Stock and Performance Shares Restricted stock generally vests over a three or five-year period.
Compensation expense is measured at the grant date and recognized ratably over the vesting period.
Performance share awards are granted to certain senior managers.
Each performance share award is earned or forfeited based on the level of achievement by the Company of pre-tax operating income on a per share basis
## Table 3 ##
Depreciation and amortization included in operating segment profit for the years ended December 31, 2008, 2007 and 2006 was as follows (in millions): 15.
LEASES Future minimum rental commitments under noncancelable operating leases in effect as of December 31, 2008 were $38.2 million for 2009, $30.1 million for 2010, $20.9 million for 2011, $15.9 million for 2012, $14.3 million for 2013 and $29.9 million thereafter.
Total rent expense for the years ended December 31, 2008, 2007 and 2006 aggregated $41.4 million, $37.1 million and $31.1 million, respectively.16.
COMMITMENTS AND CONTINGENCIES Intellectual Property and Product Liability-Related Litigation In July 2008, we temporarily suspended marketing and distribution of the Durom?
Acetabular Component (Durom Cup) in the U. S.  to allow us to update product labeling to provide more detailed surgical technique instructions to surgeons and implement a surgical training program in the U. S.  Following our announcement, product liability lawsuits and other claims have been asserted against us, some of which we have settled.
There are a number of claims still pending and we expect additional claims will be submitted.
We recorded a provision of $47.5 million in the third quarter of 2008, representing management’s estimate of these Durom Cup-related claims.
We increased that provision by $21.5 million in the fourth quarter of 2008.
The provision is limited to revisions within two years of an original surgery that occurred prior to July 2008.
These parameters are consistent with our data which indicates that cup loosenings associated with surgical technique are most likely to occur within that time period.
Any claims received outside of these defined parameters will be managed in the normal course and reflected in our standard product liability accruals.
On February 15, 2005, Howmedica Osteonics Corp.  filed an action against us and an unrelated party in the United States District Court for the District of New Jersey alleging infringement of U. S.  Patent Nos.6,174,934; 6,372,814; 6,664,308; and 6,818,020.
On June 13, 2007, the Court granted our motion for summary judgment on the invalidity of the asserted claims of U. S.  Patent Nos.6,174,934; 6,372,814; and 6,664,308 by ruling that all of the asserted claims are invalid for indefiniteness.
On August 19, 2008, the Court granted our motion for summary judgment of noninfringement of certain claims of U. S.  Patent No.6,818,020, reducing the number of claims at issue in the suit to five.
We continue to believe that our defenses against infringement of the remaining claims are valid and meritorious, and we intend to defend this lawsuit vigorously.
In addition to certain claims related to the Durom Cup discussed above, we are also subject to product liability and other claims and lawsuits arising in the ordinary course of business, for which we maintain insurance, subject to selfinsured retention limits.
We establish accruals for product liability and other claims in conjunction with outside counsel based on current information and historical settlement information for open claims, related fees and claims incurred but not reported.
While it is not possible to predict with certainty the outcome of these cases, it is the opinion of management that, upon ultimate resolution, liabilities from these cases in excess of those recorded, if any, will not have a material adverse effect on our consolidated financial position, results of operations or cash flows.
Government Investigations In March 2005, the U. S.  Department of Justice through the U. S.  Attorney’s Office in Newark, New Jersey commenced an investigation of us and four other orthopaedic companies pertaining to consulting contracts, professional service agreements and other agreements by which remuneration is provided to orthopaedic surgeons.
On September 27, 2007, we reached a settlement with the government to resolve all claims related to this investigation.
As part of the settlement, we entered into a settlement agreement with the U. S.  through the U. S.  Department of Justice and the Office of Inspector General of the Department of Health and Human Services (the “OIG-HHS”).
In addition, we entered into a Deferred Prosecution Agreement (the “DPA”) with the U. S.  Attorney’s Office for the District of New Jersey (the “U.
S.  Attorney”) and a Corporate Integrity Agreement (the “CIA”) with the OIGHHS.
We did not admit any wrongdoing, plead guilty to any criminal charges or pay any criminal fines as part of the settlement.
We settled all civil and administrative claims related to the federal investigation by making a settlement payment to the U. S.  government of $169.5 million.
Under the terms of the DPA, the U. S.  Attorney filed a criminal complaint in the U. S.  District Court for the District of New Jersey charging us with conspiracy to commit violations of the Anti-Kickback Statute (42 U. S. C.  § 1320a-7b) during the years 2002 through 2006.
The court deferred prosecution of the criminal complaint during the 18-month term of the DPA.
The U. S.  Attorney will seek dismissal of the criminal complaint after the 18-month period if we comply with the provisions of the DPA.
The DPA provides for oversight by a federally-appointed monitor.
Under the CIA, which has a term of five years, we agreed, among other provisions, to continue the operation of our enhanced Corporate Compliance Program, designed to promote compliance with federal healthcare program

Tables referenced above, in order (Table 0 first):
<table><tr><td></td><td colspan="2">Year Ended December 31,</td></tr><tr><td></td><td>2014</td><td>2013</td></tr><tr><td>U.S. high-grade - fixed rate</td><td>$182</td><td>$199</td></tr><tr><td>U.S. high-grade - floating rate</td><td>51</td><td>25</td></tr><tr><td>Total U.S. high-grade</td><td>175</td><td>190</td></tr><tr><td>Other credit</td><td>311</td><td>311</td></tr><tr><td>Liquid products</td><td>43</td><td>45</td></tr><tr><td>Total</td><td>204</td><td>205</td></tr></table>
<table><tr><td></td><td>2014</td><td>2013</td><td>2012</td></tr><tr><td>Expected life (years)</td><td>5.0</td><td>9.9</td><td>5.0</td></tr><tr><td>Risk-free interest rate</td><td>1.7%</td><td>1.9%</td><td>0.7%</td></tr><tr><td>Expected volatility</td><td>35.5%</td><td>44.3%</td><td>48.2%</td></tr><tr><td>Expected dividend yield</td><td>1.0%</td><td>1.2%</td><td>1.2%</td></tr></table>
<table><tr><td></td><td></td><td>Weighted-</td><td>Remaining</td><td></td></tr><tr><td></td><td>Number of</td><td>Average</td><td>Contractual</td><td></td></tr><tr><td></td><td>Shares</td><td>Exercise Price ($)</td><td>Term</td><td>Intrinsic Value ($) (In thousands)</td></tr><tr><td>Outstanding at December 31, 2011</td><td>2,927,737</td><td>9.42</td><td></td><td></td></tr><tr><td>Granted</td><td>13,292</td><td>32.45</td><td></td><td></td></tr><tr><td>Canceled</td><td>—</td><td>—</td><td></td><td></td></tr><tr><td>Exercised</td><td>-1,511,207</td><td>5.64</td><td></td><td></td></tr><tr><td>Outstanding at December 31, 2012</td><td>1,429,822</td><td>13.62</td><td></td><td></td></tr><tr><td>Granted</td><td>51,597</td><td>41.75</td><td></td><td></td></tr><tr><td>Canceled</td><td>-4,348</td><td>33.84</td><td></td><td></td></tr><tr><td>Exercised</td><td>-256,622</td><td>12.33</td><td></td><td></td></tr><tr><td>Outstanding at December 31, 2013</td><td>1,220,449</td><td>15.01</td><td></td><td></td></tr><tr><td>Granted</td><td>382</td><td>63.07</td><td></td><td></td></tr><tr><td>Canceled</td><td>-41,071</td><td></td><td></td><td></td></tr><tr><td>Exercised</td><td>-165,340</td><td>15.85</td><td></td><td>7,518</td></tr><tr><td>Outstanding at December 31, 2014</td><td>1,014,420</td><td>13.81</td><td>3.1</td><td>58,731</td></tr><tr><td>Exercisable at December 31, 2014</td><td>928,813</td><td>13.05</td><td>2.9</td><td>54,482</td></tr></table>
<table><tr><td></td><td>2008</td><td>2007</td><td>2006</td></tr><tr><td>Americas</td><td>$78.5</td><td>$66.9</td><td>$56.7</td></tr><tr><td>Europe</td><td>57.0</td><td>60.7</td><td>46.5</td></tr><tr><td>Asia Pacific</td><td>25.6</td><td>22.7</td><td>18.7</td></tr><tr><td>Global operations and corporate functions</td><td>114.0</td><td>79.7</td><td>75.5</td></tr><tr><td>Total</td><td>$275.1</td><td>$230.0</td><td>$197.4</td></tr></table>

Question: what was the percentage change in total rent expense from 2006 to 2007?
Answer: 0.19293
Reasoning program: subtract(37.1,31.1), divide(#0,31.1)