How to read a price history

What the line shows

Over time, the line shows the lowest total price (price plus known shipping) that we tracked for an offer that was in stock. Every time an offer's price changes we record it, so a flat stretch means the lowest tracked price did not change during that time.

We only draw the line where we really have data. It is never extended backwards into the time before we started watching a product.

Low, typical and high

The table under the chart gives the low, the high and the typical price for 30, 90, 180 and 365 days. “Typical” is the time-weighted median: a price that applied for one day counts far less than one that applied for two months, so a short spike does not distort the picture.

We only show a period when there is enough data: at least seven days and at least half of the period. If a period is not fully covered, the table says how many days of data it rests on.

Why our numbers can differ from a shop's advertised discount

Shops advertise reductions against their own reference price. Our statements such as “11% below the typical price” are something else: our own calculation over prices we tracked across several merchants. They say nothing about what a particular merchant charged before.

For context, and not legal advice: in Germany, a merchant that advertises a price reduction generally has to state the lowest price of the previous 30 days as well. Together the two give you a better picture than either number alone.

What a price history cannot do

A history shows the past. It does not predict where the price goes next.

• For new products the history is short. We say so, and we do not show periods the data cannot support.
• We only compare merchants we track. “Lowest tracked price” therefore does not mean “lowest price in Germany”.