Korea’s exports surged more than 70 percent in the third quarter from a year earlier, but much of the growth was concentrated among a handful of large corporations, widening the gap between major exporters and smaller businesses, government data showed Tuesday. While shipments soared, the number of exporting firms remained virtually unchanged, suggesting that the benefits of the export boom have yet to spread across the business sector. According to preliminary trade statistics released by the Ministry of Data and Statistics and the Korea Customs Service, exports jumped 72.3 percent year-on-year to $318.6 billion in the third quarter. Imports rose 25 percent to $203.1 billion. Export growth accelerated from 38.4 percent in the first quarter of this year and 57.2 percent in the second. “Driven by the semiconductor sector, export value and export growth reached record highs,” a ministry official said. However, the figures revealed a stark disparity in export performance by company size. Exports by large corporations more than doubled to $248.6 billion, up 103.5 percent from a year earl