Next slide please. Before we move onto the earnings results, please take a minute to read the disclaimer. I would like to remind everyone that results are based on consolidated IFRS Accounting Standards and are un-audited.
Next slide please. This conference call will take about an hour. Before we go into the Q&A session, please allow me to highlight our fourth quarter results, performance highlights, and outlook.
Moving on to revenue and profits on the next slide, revenue was (Won) 6.6 trillion, up 5% quarter-on-quarter. We did better than expected in U.S. end of year sales, higher value-added products such as FPR 3D and Smart device sales growth resulting 4% quarter-on-quarter increase in shipments.
Although panel prices slightly dropped in Q4, the price remained flat this November with the conservative inventory policies and utilization adjustment across the industry. Increased proportion of high-end specialty product, higher utilization rate and continued cost reduction significantly improved operating loss compared to previous quarter recording (Won) 145 billion growth. Operating margin was minus 2%. EBITDA margin was 13%. Income before tax was minus (Won) 133 billion. Net income was minus (Won) 6 billion.
Moving on to slide four, looking at our financial positions and ratios. Following the rough quarter, aggressive cost reduction efforts and preemptive inventory level control improved our financial position. So our cash and cash equivalent rose to (Won) 2.3 trillion. Inventories fell by (Won) 52 billion to (Won) 2.3 trillion. Net debt-to-equity ratio fell by three percentage point quarter-on-quarter recording 22%.
Moving onto slide five, looking at our cash flow. Cash at the beginning of the quarter was (Won) 2 trillion. Cash flow from operating activities resulted in cash inflow of (Won) 1.5 trillion with (Won) 638 billion increase in working capital. Cash flow from investing activities resulted in an outflow of (Won) 1.2 trillion. As a result, the net change in cash was inflow over (Won) 300 billion.