equity in net earnings of affiliated companies equity income from the m-i swaco joint venture in 2010 represents eight months of equity income through the closing of the smith transaction . interest expense interest expense of $ 298 million in 2011 increased by $ 91 million compared to 2010 primarily due to the $ 4.6 billion of long-term debt that schlumberger issued during 2011 . interest expense of $ 207 million in 2010 decreased by $ 14 million compared to 2009 primarily due to a decline in the weighted average borrowing rates , from 3.9% ( 3.9 % ) to 3.2% ( 3.2 % ) . research & engineering and general & administrative expenses , as a percentage of revenue , were as follows: .

2011: research & engineering: -2.7
general & administrative: -1.1
2010: research & engineering: -3.3
general & administrative: -1.1
2009: research & engineering: -3.5
general & administrative: -1.1

although research & engineering decreased as a percentage of revenue in 2011 as compared to 2010 and in 2010 compared to 2009 , it has increased in absolute dollars by $ 154 million and $ 117 million , respectively . these increases in absolute dollars were driven in large part by the impact of the smith acquisition . income taxes the schlumberger effective tax rate was 24.4% ( 24.4 % ) in 2011 , 17.3% ( 17.3 % ) in 2010 , and 19.6% ( 19.6 % ) in 2009 . the schlumberger effective tax rate is sensitive to the geographic mix of earnings . when the percentage of pretax earnings generated outside of north america increases , the schlumberger effective tax rate will generally decrease . conversely , when the percentage of pretax earnings generated outside of north america decreases , the schlumberger effective tax rate will generally increase . the effective tax rate for both 2011 and 2010 was impacted by the charges and credits described in note 3 to the consolidated financial statements . excluding the impact of these charges and credits , the effective tax rate in 2011 was 24.0% ( 24.0 % ) compared to 20.6% ( 20.6 % ) in 2010 . this increase in the effective tax rate , excluding the impact of the charges and credits , was primarily attributable to the fact that schlumberger generated a larger proportion of its pretax earnings in north america in 2011 as compared to 2010 as a result of improved market conditions and the effect of a full year 2019s activity from the acquired smith businesses . the effective tax rate for 2009 was also impacted by the charges and credits described in note 3 to the consolidated financial statements , but to a much lesser extent . excluding charges and credits , the effective tax rate in 2010 was 20.6% ( 20.6 % ) compared to 19.2% ( 19.2 % ) in 2009 . this increase is largely attributable to the geographic mix of earnings as well as the inclusion of four months 2019 results from the acquisition of smith , which served to increase the schlumberger effective tax charges and credits schlumberger recorded significant charges and credits in continuing operations during 2011 , 2010 and 2009 . these charges and credits , which are summarized below , are more fully described in note 3 to the consolidated financial statements. .

Questions:
what was the change in research & engineering as a percent of revenue from 2010 to 2011?
and what was the value of research & engineering as a percent of revenue in 2010?
how much, then does that change represent in relation to this value, in percentage?

Answers:
-0.6
3.3
-18.2%