Taleb is concerned with black swans, i.e., unpredictable and improbable events that have great impact. Among the examples of these he cites are the rapid spread of the Internet and the 9/11 attacks. People endeavor to explain black swans after they occur, but they cannot do so in advance. Despite the crucial effects of these events, economists and other supposed experts in prediction fail to allow for them. Because of this failure, Taleb maintains that much business forecasting is useless.