Pierre-Olivier Gourinchas and Philippe Martin claim that their calculations suggest that Hollande's cost-shifting from payrolls to the state budget will increase exports by 3% and raise aggregate demand by 0.75%. Hence the responsibility pact is not, as critics such as Paul Krugman (and I, in one of my moods) have charged, a contribution to austerity policy but rather a Keynesian policy in austerian drag (as I argued in a different mood).
Frankly, I don't know who's right. Gourinchas, Martin, and Krugman are all reputable economists, and I, at best a disreputable economist, don't even agree with myself. A lot depends on the details of timing, about which Gourinchas and Martin don't tell us much.