periodoverperiod

Period-over-period (PoP) is a method of comparing a metric's value in one period to the value in the immediately preceding period to measure growth or change. It is a common way to assess momentum and short-term performance across many domains, including finance, sales, and web analytics.

Calculation and interpretation are straightforward: PoP change = (Current period value − Previous period value) / Previous period value × 100%. Periods should be comparable in length and context; for example, a calendar month to the previous calendar month, or a quarter to the previous quarter. Seasonality or holidays can affect results, so analysts may use seasonally adjusted data or smoothing when appropriate.

Common variants include month-over-month (MoM), quarter-over-quarter (QoQ), week-over-week, and day-over-day comparisons. Year-over-year (YoY) is related and compares non-consecutive periods (such as this quarter vs. last year's quarter) and is sometimes treated as a PoP measure.

Applications of PoP analysis include monitoring business performance, evaluating marketing campaigns, tracking inventory turnover, and observing user engagement trends. It helps identify momentum, set near-term targets, and respond quickly to changes in conditions.

Limitations and cautions: PoP can be distorted by seasonality, holidays, or one-off events; comparing periods with differing lengths or data collection methods can be misleading; small numbers produce high volatility; and changes in measurement can affect results. Best practices include using longer horizons for context, reporting both absolute values and percentage changes, and applying smoothing or decomposition for noisy data.

Example: revenue of $100,000 in May versus $90,000 in April yields a PoP growth of (100,000 − 90,000) / 90,000 × 100% = 11.1%.