Lookback period

How it works

Many market-priced financings do not use a single day's price. Instead they define a window, for example "the five trading days immediately preceding the conversion date", and take a statistic from it: the average VWAP, the lowest VWAP, the lowest closing price, or the lowest intraday trade. That window is the lookback period.

Equity lines use short pricing periods (often one to three days) to set each purchase price. Variable-price conversions on notes or preferred stock commonly use longer windows of ten to twenty trading days.

Why the length and statistic matter

The combination of a long window and a "lowest price" statistic lets the conversion price reflect the cheapest moment in the window, even if the stock has recovered since. A short window or an average statistic tracks the current price more closely.

Worked example

Hypothetical: Company X's closing prices over ten trading days ran from $1.50 down to $1.10 and back up to $1.45 today. A note converts at 80% of the lowest closing price in the lookback period.

All figures are hypothetical.

With the ten-day window, the holder converts at $0.88 while the stock trades at $1.45, a 39% gap, compared with a 24% gap under the three-day window.

How to spot it

In the note or certificate of designation, find the defined terms "Conversion Price", "Measurement Period" or "Trading Day", and read which statistic is used ("lowest", "average", "closing", "VWAP"). Pair it with the VWAP discount to understand the full formula. See Toxic convertibles.