The Overnight Policy Rate

The overnight policy rate (or 'overnight rate') is the interest rate the Bank of Canada targets for very short-term (overnight) loans between banks. It's the Bank's primary tool for implementing monetary policy: raising it makes borrowing more expensive economy-wide to cool inflation, and cutting it makes borrowing cheaper to stimulate growth.

Because it's administered directly by the Bank rather than set by the market, it only moves on scheduled announcement dates. This site flags every date the rate actually changed as a 'policy shock' in its Gold-layer data.