The frame for a given survey is the subset of the frozen frame, comprising the set of units that match the specification of the survey target population. Thus, for example, a survey of employment will include units in all (or at least most) industries that are employers, i.e., will exclude units that are non-employers. A survey of manufacturing will include all units that have an ISIC code in the manufacturing group, whether they have employees or not. A survey of capital expenditure may include all units above a certain size. Thus the survey frames are typically different from one another but may be extracted from the same common set of units, i.e. a frozen frame. A frame may be referred to as a survey frame also as a sampling frame or a survey sampling frame.