| Census (Registrar General and Census Commissioner, MHA) | Complete enumeration, house‑listing then population enumeration | Decennial; last completed 2011; Census 2027 under way (reference date 1 March 2027; 1 October 2026 for snow‑bound areas) | Universal; small‑area data; denominators | Infrequent; under‑counting; postponed 2021 round |
| Civil Registration System (RBD Act 1969, amended 2023) | Compulsory registration within 21 days | Continuous | Legal documents; potentially complete | Incomplete in some states, especially deaths and infant deaths; cause of death often unreliable |
| Sample Registration System (since 1964–65 pilot; full scale 1969–70) | Dual record system: continuous enumeration + independent half‑yearly survey, matched | Annual | Reliable national and state vital rates (CBR, CDR, IMR, TFR, MMR special bulletins) | Sample‑based; limited district estimates |
| NFHS (MoHFW; IIPS Mumbai nodal) | Multistage household survey (DHS model) | NFHS‑1 1992–93 … NFHS‑5 2019–21, NFHS‑6 2023–24 (released May 2026) | District‑level health, nutrition, FP, biomarkers | Cross‑sectional; recall; reduced indicator list in NFHS‑6 fact sheet |