Coverage window

Also seen as: first price date, last price date, price history depth

Why can one recent instrument shorten a whole backtest?

Because an instrument has no prices to contribute on the dates before its coverage window begins. Nothing about the run is invalid, but only the stretch that sits inside every instrument's coverage window tests the full set you designed on real prices for all of them. The shortest coverage window among your instruments is therefore the real limit on any strategy that depends on all of them.

This is easy to miss because Fincanva does not move your chosen simulation start year forward to match a short coverage window — the year you enter is the year the run starts, so the mismatch is not announced at the moment you choose it. Metrics are still computed across the whole window you asked for, which is exactly why a long-history headline figure can belong to a strategy that could only have existed for part of it. Check the first price date of anything recent before reading a long-history result.

Defaults in Fincanva

• Every instrument carries a first price date and a last price date; together they are its coverage window.
• A backtest's end date follows the newest available market data rather than today's calendar date, so the catalogue's latest price date — not the clock — closes a run. See data freshness and frontier.
• A delisted instrument's coverage window ends at its last traded date. The instrument stays in the catalogue and stays usable for the period it did trade.
• A run only reads an instrument from its own simulation start year onward, so history deeper than the year you pick sits outside the run — the setting defaults to 2000 but reaches back further; see simulation start year.

Worked example

A strategy pairs a broad US equity ETP whose prices reach back to 1993 with a thematic ETF that launched in March 2021, and the start year is set to 2000. Inside the run the equity ETP has 26 years of coverage; the thematic ETF has just over five, all of it after March 2021. Roughly four-fifths of the backtest's calendar therefore predates the second instrument's coverage window entirely, and only the stretch from 2021 onward tests the pair as designed.

The headline CAGR and max drawdown are still reported over the full window, so a reader who does not check the ETF's first price date will attribute two decades of behavior to a combination that could only have run for five years of it. Reading the coverage windows first tells you which figure you are actually looking at.