Starting a business is a challenging endeavor, and certain industries are known to be particularly tough due to various factors such as high competition, high capital requirements, complex regulations, and rapidly changing market dynamics. Here are some of the toughest businesses to start:

1. Restaurants: The restaurant industry is notoriously difficult due to high failure rates, intense competition, and slim profit margins. According to a study by Ohio State University, 60% of restaurants fail within their first year, and 80% fail within the first five years. The challenges include high operating costs, inventory management, staff turnover, changing consumer preferences, and the need for consistent quality and service.

Example: The restaurant industry has seen several high-profile failures, such as the bankruptcy of chains like Bennigan's and Sbarro, and the closure of celebrity chef Gordon Ramsay's restaurant in New York City.

Reference: https://www.eater.com/2018/5/10/17327790/restaurant-failure-rate-stats

2. Retail clothing stores: The retail industry, especially clothing stores, faces intense competition from e-commerce giants and changing consumer behavior. The rise of online shopping has significantly impacted brick-and-mortar stores, leading to store closures and bankruptcies. The challenges include high inventory costs, managing fashion trends, maintaining foot traffic, and providing a unique shopping experience.

Example: Retailers like Forever 21 and Payless ShoeSource filed for bankruptcy in recent years due to declining sales and the inability to adapt to changing consumer preferences.

Reference: https://www.businessinsider.com/retailers-closing-stores-in-2020-2020-1

3. Tech startups: While the tech industry offers immense potential for innovation and growth, it is also highly competitive and capital-intensive. Tech startups often face challenges such as securing funding, attracting and retaining top talent, rapidly evolving technologies, and fierce competition from established players. Additionally, the failure rate for startups in general is high, with only a small percentage achieving long-term success.

Example: Quibi, a short-form streaming service, raised $1.75 billion in funding but shut down within six months due to low subscriber numbers and a crowded streaming market.

Reference: https://www.cnbc.com/2020/10/21/how-quibi-went-from-hollywoods-hottest-start-up-to-a-2point1-billion-flop.html

4. Biotechnology and pharmaceuticals: The biotech and pharmaceutical industries are highly regulated and require significant investments in research and development. Developing new drugs or medical technologies involves lengthy clinical trials, strict regulatory approvals, and high costs. The success rate for new drug development is low, with estimates ranging from 10% to 20%.

Example: Theranos, a once-promising blood-testing startup, faced regulatory scrutiny and collapsed after it was revealed that its technology did not work as claimed.

Reference: https://www.nytimes.com/2018/03/14/technology/elizabeth-holmes-theranos.html

5. Airlines: The airline industry is capital-intensive, highly regulated, and vulnerable to external factors such as fuel prices, economic downturns, and geopolitical events. Operating costs, including aircraft, maintenance, fuel, and labor, are significant. Intense competition, price wars, and unpredictable demand further contribute to the challenges faced by airlines.

Example: Many airlines, including Pan Am, Eastern Air Lines, and WOW Air, have filed for bankruptcy or ceased operations due to financial difficulties.

Reference: https://www.businessinsider.com/airlines-that-went-bankrupt-2020-10

Starting a business in any industry requires careful planning, market research, and adaptability to overcome challenges. While these industries are considered tough, success can still be achieved with a solid business plan, innovative strategies, and a deep understanding of the market.