As with demand elasticities there is a time dimension to the responsiveness of supply to a change in price, referred to as a supply lag. Other things being equal, the longer the time period the greater the value of Es. For example , immediately following a price increase existing producers might be incapable of increasing supply unless they have unsold stock and the value of Es might approach zero, the supply curve being nearly vertical. In the next period, the firm might hire extra workers to work with existing capacity, or use the existing workforce on overtime Supply therefore increases. It may also be possible to shift resources from producing one commodity to another. Thus as the price of lager rises relative to beer, then beer-producing facilities might move over to lager. Eventually, supply might increase even further as new firms join the industry ion plans. and existing firms fully adjust to new production plans. Certain firms might be able to adjust supply relatively quickly to price changes. However, particularly when using relatively specialized factors of production, which might immediately be in short supply, adjustments in supply might be more gradual. For example, an increase in the wages offered to dentists would have little Immediate impact upon supply. However, in the longer time period this might encourage more persons to seek dental training, and allow dental schools the opportunity to provide extra places.