ISM Manufacturing Index is to evaluate the US economy by investigating executives' expectations of future production, new orders, inventory, employment and delivery. Although the manufacturing industry accounts for a small proportion of GDP, the fluctuation of manufacturing industry plays an important role in the change of GDP. Therefore, the development of manufacturing industry usually precedes the overall economy, making ISM manufacturing index a leading indicator of economic reversal. After a period of recession, the demand for manufacturing products has accelerated, and the ISM manufacturing index has risen, which is likely to imply that the economy will turn upward. On the contrary, during the period of economic expansion, manufacturing orders and production slowed down, indicating a slowdown in the economy. ISM manufacturing survey has attracted much attention because of its timeliness. Analysts pointed out that ISM is expected to become one of the most important data to promote market volatility when economic expansion slows down. The dispute lies in ISM's payment price index and employment segmentation. These two sub-items reflect confidence in inflation and working conditions-the two most important indicators of economic health. In view of the timeliness of ISM, the information disclosed by these sub-items takes precedence over other data (such as non-agricultural employment report or CPI), making ISM an important indicator. The data are basically published in the form of diffusion indicators. For each sub-item (production, new order, etc.). ), the expected "increase" percentage of respondents plus half of the expected "unchanged" percentage, MINUS the expected "decrease" percentage, and the final sum of the sub-items is the ISM manufacturing index. Data above 50 generally indicate expansion, and data below 50 indicate recession.