The trending term "kill line" actually originates from the Federal Reserve's *Report on the Economic Well-Being of U.S. Households* (2024 edition, based on survey data from October 2024, published in May 2025). The report shows that only 63% of U.S. adults said they could handle a $400 emergency expense using cash, savings, or a credit card (paid off in full the next month). This means the remaining 37% are unable to handle this "400-dollar emergency expense" in such a way. The "400-dollar emergency expense" is a long-tracked financial vulnerability metric in this report and is often seen as the "bottom line" or "kill line" for economic stress among Americans. It reflects how many households lack a financial buffer, where a small unexpected event (like car repairs or medical bills) could lead to a financial crisis. It reminds me of what former Chinese Premier Li Keqiang said back in 2020—that 600 million Chinese people have a monthly income of less than 1,000 yuan. This also means that this group has very weak risk resilience. The "kill line" serves as a wake-up call for ordinary people: try to earn as much as possible, but also stay clear-headed and set aside some emergency savings. Don’t let a sudden incident choke your cash flow. This is the baseline mindset for life—always leave yourself enough of a safety cushion!