Data journalism has a long history but is increasingly important as algorithms and data play a larger role. Newspapers have used data for centuries, and tools like calculators, mainframes, spreadsheets and databases helped early computer-assisted reporting. Today, data journalism uses online tools to gather, clean, analyze and visualize data to support investigative reporting. Emerging trends include using open data to monitor issues like corruption, using sensors and drones to collect real-time data, and ensuring accountability and transparency around the use of personalized data and predictive algorithms. When combined with responsive institutions, data journalism can help drive social change.