As noted above, there are three elements to the Force Index. First, there is either a positive or negative price change. A positive price change signals that buyers were stronger than sellers, while a negative price change signals that sellers were stronger than buyers. Second, there is the extent of the price change, which is simply the current close less the prior close. The "extent" shows us just how far prices moved. A big advance shows strong buying pressure, while a big decline shows strong selling pressure.