From a quick scan of the article the chart is based on figure 1. p-value for the more disadvantaged group is 0.017 for the less disadvantaged it's 0.02. There's a 3rd group, 'medium disadvantaged', which has a horizontal line.
The trend is more obvious when the points for the individual groups are separated out, but it does seem to me that a small number of points at the extremes might account for slope - if you removed one or two key points from each group the slopes might go away.
The trend is more obvious when the points for the individual groups are separated out, but it does seem to me that a small number of points at the extremes might account for slope - if you removed one or two key points from each group the slopes might go away.