When the signal is unavailable
We need at least 30 recorded prices, a usable weekly comparison and a usable premium average. Prices must be no more than 4 London calendar days old, with no latest price movement awaiting review. Weekends and holidays count; an old price does not by itself mean an exchange publication was missed.
How Buy, Hold and Watch are selected
Combined means LME + premium. A “30-price average” uses the latest 30 recorded prices, not 30 calendar days. Rules are checked in this order, using unrounded values:
- Buy: combined is below its 30-price average, its 7-price direction is not Up, and its 14-price dispersion is not High.
- Hold: combined is more than 2.5% above its 30-price average; or all three apply: its 7-price direction is Up, premium is above its own 30-price average, and the weekly combined increase is more than 0.8%.
- Watch: neither rule above applies.
What the comparisons mean
- Recent direction: compare the first and last of the latest 7 recorded prices. A change smaller than $0.01 in either direction is Flat; otherwise it is Up or Down.
- Price spread (dispersion): the population standard deviation of the latest 14 combined price levels, divided by their average, × 100. Below 1.1% is Low; 1.1% to below 2.2% is Medium; 2.2% or above is High. This measures price levels, not daily returns, and is not a validated purchasing-risk rating.
- Weekly change: compare with the newest recorded price on or before 7 calendar days before the latest price, no more than 10 days before it. Missing dates are not filled or estimated.
Which price movements need review?
An LME or premium change greater than 10% since the previous recorded price needs review. Exactly 10% does not. A premium changing from zero to positive also needs review. Only a flag on the latest price withholds the current signal; older flags do not.
Calculation behind the current result
“What changed?” explains the price difference between two dates. That difference alone does not determine Buy, Hold or Watch.