In contrast to time-series data, cross-section data record the values of different variables at a point in time. Table 2.2 contains a cross-section of unemployment rates for Canada and Canadian provinces economies. For January 2012 we have a snapshot of the provincial economies at that point in time, likewise for the months until June. This table therefore contains repeated cross-sections.
When the unit of observation is the same over time such repeated cross sections are called longitudinal data. For example, a health survey that followed and interviewed the same individuals over time would yield longitudinal data. If the individuals differ each time the survey is conducted, the data are repeated cross sections. Longitudinal data therefore follow the same units of observation through time.
| Jan | Feb | Mar | Apr | May | Jun | |
| CANADA | 7.6 | 7.4 | 7.2 | 7.3 | 7.3 | 7.2 |
| NFLD | 13.5 | 12.9 | 13.0 | 12.3 | 12.0 | 13.0 |
| PEI | 12.2 | 10.5 | 11.3 | 11.0 | 11.3 | 11.3 |
| NS | 8.4 | 8.2 | 8.3 | 9.0 | 9.2 | 9.6 |
| NB | 9.5 | 10.1 | 12.2 | 9.8 | 9.4 | 9.5 |
| QUE | 8.4 | 8.4 | 7.9 | 8.0 | 7.8 | 7.7 |
| QNT | 8.1 | 7.6 | 7.4 | 7.8 | 7.8 | 7.8 |
| MAN | 5.4 | 5.6 | 5.3 | 5.3 | 5.1 | 5.2 |
| SASK | 5.0 | 5.0 | 4.8 | 4.9 | 4.5 | 4.9 |
| ALTA | 4.9 | 5.0 | 5.3 | 4.9 | 4.5 | 4.6 |
| BC | 6.9 | 6.9 | 7.0 | 6.2 | 7.4 | 6.6 |
Source: Statistics Canada CANSIM Table 282-0087
Cross-section data: values for different variables
recorded at a point in time.
Longitudinal data: follow the same units of
observation through time.
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