While the rationale behind risk parity is well understood, the implementation frameworks often differ. For example, some implementations are purely passive while others are more active, the way risk is defined can differ, and the underlying instruments used can vary.
In 2018, the S&P Risk Parity Indices became the first transparent, rules-based benchmarks offered in the space. Since their launch, several firms have adopted these indices as benchmarks and for replication.
You can now read the full whitepaper at the link below