This is a zero sum graph, as market share must add to 100%. You may observe that the one large decrease in Windows market share occurs at the same time as three small increases for Mac OS, Linux, and “unknown”.
Nothing else increased. The three small increases must be equal to the Windows decrease.
I’m not seeing much of an increase there for Mac or Linux. I’m not sure how you drew those conclusions from this graph.
This is a zero sum graph, as market share must add to 100%. You may observe that the one large decrease in Windows market share occurs at the same time as three small increases for Mac OS, Linux, and “unknown”.
Nothing else increased. The three small increases must be equal to the Windows decrease.