Using redshift space distortion data, we perform model-independent
reconstructions of the growth history of matter inhomogeneity in the expanding
Universe using two methods: crossing statistics and Gaussian processes. We then
reconstruct the corresponding history of the Universe background expansion and
fit it to type Ia supernovae data, putting constraints on
$(Ømega_m,0,\sigma_8,0)$. The results obtained are consistent with
the concordance flat-$Łambda$CDM model and General Relativity as the gravity
theory given the current quality of the inhomogeneity growth data.