Change vs Difference
1 gives you the percentage point (p.p.) difference,
2 gives you the percentage difference.
There is no rule that says that if you're dealing with shares, you have to use 1. The reason 1 is preferred is that, when the measurement unit is in percentage, things get confusing quickly (e.g. going from a 2% to a 1% interest rate is a 50 percent reduction in the interest rate, but of course only a 1 p.p. reduction).
In your case, 2 could be meaningful, though. For example, &quot;the share in labor employed in manufacturing decreased by half&quot;. A compromise could be to express the change in percentage points to avoid confusion, and then add the percentage change if it is meaningful (e.g. the labor share decreased by 20 p.p., a reduction of 50%).