  Reasons for the emergence of Chebyshev's bias were investigated. The Deep
Riemann Hypothesis (DRH) enables us to reveal that the bias is a natural
phenomenon for achieving a well-balanced disposition of the whole sequence of
primes, in the sense that the Euler product converges at the center. By means
of a weighted counting function of primes, the authors succeed in expressing
magnitudes of the deflection by a certain asymptotic formula under the
assumption of DRH, which provides a new formulation of Chebyshev's bias. For
any Galois extension of global fields and for any element $\sigma$ in the
Galois group, we have established a criterion of the bias of primes whose
Frobenius elements are equal to $\sigma$ under the assumption of DRH. As an
application we have obtained a bias toward non-splitting and non-principle
primes in abelian extensions under DRH. In positive characteristic cases, DRH
is known, and all these results hold unconditionally.
