Wafer starts
The number of silicon wafers that begin processing in a fab during a period, a leading indicator of future chip output and demand.
A wafer start is a silicon wafer that enters a fab and begins processing. Chips take several weeks to months to move through a fab, so wafer starts lead shipments by a period. Foundries and industry bodies report starts, and monthly figures are noisy, so the trend matters more than any single month.
Traders care because rising starts can signal that customers are placing confident orders, while falling starts can precede weaker shipments. Starts do not measure sales, so pair them with inventory levels, pricing and utilization. A foundry may also start wafers ahead of demand to secure capacity.
Worked example (illustrative numbers, not real data): a fab starts 100,000 wafers in one quarter, up from 90,000 a quarter earlier. If the cycle from start to shipment takes about one quarter, all else equal, that points to higher shipments in the following quarter.