Markets opened flat on Wednesday morning ahead a busy day on the economic calendar with all eyes focusing on growth data and a policy decision in the US later on.The world's biggest economy is expected to have grown at an annualised rate of 1.1% in the fourth quarter of 2012, according to preliminary estimates due for release at 13:30 (London time), well below the 3.1% growth in the third quarter. Meanwhile, the Federal Open Market Committee (FOMC) will reveal its policy decision at 19:15 after a two-day meeting in Washington. While markets will keep a close eye on the announcement, analysts have labelled this as the most anticipated "non-event" of the week. "We think this Fed meeting is a complete non-event," said the experts at Jefferies. While the economy continues to slug along, the improvements seen in recent data are said to be insufficient to force the Fed to move its hand. As such, the central bank is expected to continue with its stimulus measures but everyone will be looking out for comments on when the current third round of quantitative easing (QE) will end. Most expect the Fed to continue through with QE3 until the end of the year, if not early 2014. "Subdued start to a busy session for European markets Wednesday with traders holding fire ahead of some key economic releases. Earnings today are also a mixed bag, adding to the general lack of conviction to get involved," said market strategist Ishaq Siddiqi from ETX Capital.FTSE 100: Petrofac sinks on Algerian concernsOilfield services group Petrofac sank in early trading on reports that it has halted activities at the In Salah gas compression project in Algeria. According to Algeria's Echorouk online newspaper, said that this was related to a terrorist attack at the natural-gas plant.Tobacco giant Imperial also suffered sharp falls after saying that its Finance Director is to retire. The company also revealed that operating profits would fall in the first half as "market trends have worsened in a number of key markets including in the EU and Russia."Oil group BP was higher after a US court accepted an agreement to plead guilty for its role in the Deepwater Horizone explosion and oil spill in 2010.Water United Utilities was higher despite saying that revenue increased at a rate "slightly below the slowed regulated price rise for 2012/13".Chemicals group Johnson Matthey was in the red after saying that both sales and profits fell in the third quarter. The firm said that volumes in the Precious Metals division had been hit by Amplats' plan to close mines in South Africa.Mining group Antofagasta was a heavy faller as the wider mining sector was out of favour despite the company posting strong production results in the fourth quarter. Sector peer Polymetal was also lower even though it topped production guidance in 2012.FTSE 250: Renishaw sinks after first-half resultsPrecision tool maker Renishaw fell despite reporting a sharp increase in first-half earnings as it was boosted by a string of large consumer electronics orders in China. However, the company cautioned it faces tough financial comparators in the second half.Titanium feedstock miner Kenmare Resources rose after saying that revenue rose 40% in 2012.Chip designer Imagination Tech was a high riser after Morgan Stanley upgraded the stock to 'overweight'.FTSE 100 - RisersWPP (WPP) 1,000.00p +2.30%ARM Holdings (ARM) 881.00p +1.32%United Utilities Group (UU.) 749.50p +1.28%Bunzl (BNZL) 1,120.00p +1.27%Prudential (PRU) 967.50p +1.26%Sage Group (SGE) 328.60p +1.11%Reckitt Benckiser Group (RB.) 4,303.00p +1.06%Legal & General Group (LGEN) 153.20p +0.99%RSA Insurance Group (RSA) 132.90p +0.99%Associated British Foods (ABF) 1,751.00p +0.92%FTSE 100 - FallersPetrofac Ltd. (PFC) 1,614.00p -7.08%Antofagasta (ANTO) 1,211.00p -5.02%Imperial Tobacco Group (IMT) 2,355.00p -4.50%Johnson Matthey (JMAT) 2,345.00p -2.62%Amec (AMEC) 1,071.00p -2.55%Polymetal International (POLY) 1,086.00p -2.16%Wood Group (John) (WG.) 812.50p -1.34%Kazakhmys (KAZ) 758.00p -1.11%BG Group (BG.) 1,139.00p -1.04%British American Tobacco (BATS) 3,267.50p -1.03%FTSE 250 - RisersPhoenix Group Holdings (DI) (PHNX) 640.00p +8.29%Imagination Technologies Group (IMG) 474.00p +7.36%Kenmare Resources (KMR) 34.80p +3.29%Oxford Instruments (OXIG) 1,625.00p +2.07%Perform Group (PER) 390.00p +1.85%3i Group (III) 271.30p +1.69%Redrow (RDW) 195.80p +1.50%Workspace Group (WKP) 326.90p +1.21%Inmarsat (ISAT) 642.00p +1.10%Unite Group (UTG) 285.00p +1.06%FTSE 250 - FallersRenishaw (RSW) 1,861.00p -5.05%Fenner (FENR) 395.40p -4.26%Devro (DVO) 338.00p -2.51%Chemring Group (CHG) 282.70p -2.48%Centamin (DI) (CEY) 51.70p -2.27%Lonmin (LMI) 319.10p -2.00%Tullett Prebon (TLPR) 246.50p -1.83%Stobart Group Ltd. (STOB) 98.15p -1.75%Alent (ALNT) 340.00p -1.73%Mitchells & Butlers (MAB) 299.30p -1.68%BC