NVR Inc. /zigman2/quotes/209548385/composite NVR +0.03% will join the S&P 500 index /zigman2/quotes/210599714/realtime SPX +0.06% this month, the second change to the index announced this week. S&P Dow Jones Indices announced the change Friday afternoon, saying that the home-builder will replace Jefferies Financial Group Inc. /zigman2/quotes/206157580/composite JEF +2.56% in the index as of Sept. 26. Jefferies is moving down to the S&P MidCap 400 index after spinning off Spectrum Brand Holdings Inc. /zigman2/quotes/209008733/composite SPB +2.51% . Earlier in the week, S&P Dow Jones Indices announced that CDW Corp. /zigman2/quotes/208546399/composite CDW -0.02% will also move into the S&P 500 this month, replacing Total System Services Inc., which has been acquired. NVR shares declined 1.2% in after-hours trading Friday.