A new phenomenological approach is suggested to determine the strangeness contents of light-flavour isoscalars. This approach is based on phenomenological laws of hadron production related to the spin, isospin, strangeness content and mass of the particles. The ``effective numbers of s and bar{s} quarks in the isoscalar partners i_1 and i_2 are given by the nonstrange-strange mixing angle phi: k(i_1)=2sin^2phi and k(i_2)=2cos^2phi. From the total production rates per hadronic Z decay of all light-flavour hadrons measured so far at LEP the values for k are found to be: k(eta) equiv 2-k(eta^{prime}) = 0.91 pm 0.12, k(phi) equiv 2-k(omega) = 1.94 pm 0.09, k(f_2^{prime}) equiv 2-k(f_2) = 1.84 pm 0.21 and k(f_0) = 0.09 pm 0.13. Our results on the eta--eta^{prime}, omega--phi and f_2--f_2^{prime} isoscalar mixing are consistent with the present experimental evidence. Quite remarkably, our value for k(eta) corresponds to the singlet-octet mixing angle theta_P = -12.4^{circ} pm 3.5^{circ}. The obtained strangeness content of the f_0(980) scalar/isoscalar is not consistent with the values supported by different model studies. However, taking the f_0(980) in our analysis with the mass of the bare state (K-matrix pole) f_0^{bare}(720 pm 100), the mixing angle is found to be: |phi_S^{bare}| = 73^{circ} pm 7^{circ} pm 24^{circ}, in good agreement with the prediction of the K-matrix analysis.
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