Openings are defined as the sum of Growth and Replacement jobs. Users sometimes attempt to mimic this calculation in Analyst by summing Change and Replacement jobs.
However, the math doesn't work out, for two reasons.
Growth and Change are defined differently. Growth is the sum of new jobs between two years, and can only be positive or 0. Growth cannot be negative. Change is the difference in job counts between two years, and can either be positive, negative, or 0. Sometimes Growth and Change happen to be equal, but often they are different, leading to problems when users attempt to add together Replacements and Change (in lieu of Growth) to equal Openings.
Growth is calculated for each individual county/occupation/class of worker/year-pair combination, whereas Change is simply an aggregate end-year figure less an aggregate start-year figure. This means that Change can be easily calculated in Analyst by subtracting the start year's job counts from the end year's job counts. However, Growth is much more complicated and can only be calculated in Analyst by looking at a single occupation in a single county for a single class of worker, for two consecutive years (e.g. 2015-2016). The result of each of these single calculations are then summed to come up with an overall Growth estimate for the user-defined parameters.
Therefore, users can use Change as a proxy for Growth in situations where only one county, one occupation, one class of worker, and two consecutive years are selected.