PMI is built from a monthly survey of purchasing managers, asking whether business conditions (new orders, output, employment, prices) are improving, worsening, or holding steady compared to the previous month. A reading above 50 signals expansion; below 50 signals contraction. Because it's survey-based rather than calculated from hard transaction data, it tends to arrive faster than official statistics — which is exactly why markets pay close attention to it as an early read on where the economy is heading.
Unlike CPI, GDP, or unemployment data — which come from government statistical agencies and are public by law — PMI is a commercial product, produced and licensed by S&P Global (for most of the world) and the ISM (for the US). It isn't free, public data, which is why we're upfront that we can't show a live PMI figure here the way we can for the indicators above, until we have a licensed data relationship in place.