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Identify Reference Periods in PNADC Data

Source: R/pnadc-identify-periods.R
pnadc_identify_periods.Rd

PNADC is a quarterly survey, but each interview actually refers to a specific temporal period within the quarter. This function identifies which month, fortnight (quinzena), and week each observation belongs to, enabling sub-quarterly time series analysis.

The algorithm uses a nested identification approach:

  • Phase 1: Identify MONTHS for all observations using:

    • IBGE's reference week timing rules (first reference week – ending in a Saturday – with sufficient days)

    • Respondent birthdates to constrain possible interview dates

    • UPA-panel level aggregation across ALL quarters (panel design)

    • Dynamic exception detection (identifies quarters needing relaxed rules)

  • Phase 2: Identify FORTNIGHTS for month-determined observations:

    • Search space constrained to 2 fortnights within determined month

    • Household-level aggregation within each quarter

  • Phase 3: Identify WEEKS for fortnight-determined observations:

    • Search space constrained to ~2 weeks within determined fortnight

    • Household-level aggregation within each quarter

Usage

pnadc_identify_periods(data, verbose = TRUE, store_date_bounds = FALSE)

Arguments

data

A data.frame or data.table with PNADC microdata. Required columns:

  • Ano: Survey year

  • Trimestre: Quarter (1-4)

  • UPA: Primary Sampling Unit

  • V1008: Household id/sequence within UPA

  • V1014: Panel identifier

  • V2008: Birth day (1-31)

  • V20081: Birth month (1-12)

  • V20082: Birth year

  • V2009: Age

Optional but recommended:

  • V2003: Person sequence within household

verbose

Logical. If TRUE (default), display progress information.

store_date_bounds

Logical. If TRUE, stores date bounds and exception flags in the crosswalk for optimization when calling pnadc_experimental_periods(). This enables 10-20x speedup for the probabilistic strategy by avoiding redundant computation. Default FALSE.

Value

A data.table crosswalk with columns:

Ano, Trimestre, UPA, V1008, V1014

Join keys (year, quarter, UPA, household, panel)

ref_month_in_quarter

Integer. Month position in quarter (1, 2, 3) or NA

ref_month_in_year

Integer. Month position in year (1-12) or NA

ref_fortnight_in_month

Integer. Fortnight position in month (1 or 2) or NA

ref_fortnight_in_quarter

Integer. Fortnight position in quarter (1-6) or NA

ref_week_in_month

Integer. Week position in month (1-4) or NA

ref_week_in_quarter

Integer. Week position in quarter (1-12) or NA

date_min

Date. Lower bound of the interview reference date for the individual. Only returned if store_date_bounds = TRUE

date_max

Date. Upper bound of the interview reference date for the individual. Only returned if store_date_bounds = TRUE

week_1_start

Date. Sunday of the IBGE first reference week of the month. Only returned if store_date_bounds = TRUE

week_1_end

Date. Saturday of the IBGE first reference week of the month. Only returned if store_date_bounds = TRUE

week_2_start

Date. Sunday of the IBGE second reference week of the month. Only returned if store_date_bounds = TRUE

week_2_end

Date. Saturday of the IBGE second reference week of the month. Only returned if store_date_bounds = TRUE

week_3_start

Date. Sunday of the IBGE third reference week of the month. Only returned if store_date_bounds = TRUE

week_3_end

Date. Saturday of the IBGE third reference week of the month. Only returned if store_date_bounds = TRUE

week_4_start

Date. Sunday of the IBGE fourth reference week of the month. Only returned if store_date_bounds = TRUE

week_4_end

Date. Saturday of the IBGE fourth reference week of the month. Only returned if store_date_bounds = TRUE

month_max_upa

Integer. Maximum month position across UPA-V1014 group (for debugging). Only returned if store_date_bounds = TRUE

month_min_upa

Integer. Minimum month position across UPA-V1014 group (for debugging). Only returned if store_date_bounds = TRUE

fortnight_max_hh

Integer. Maximum fortnight position within household (for debugging). Only returned if store_date_bounds = TRUE

fortnight_min_hh

Integer. Minimum fortnight position within household (for debugging). Only returned if store_date_bounds = TRUE

week_min_hh

Integer. Minimum week position within household (for debugging). Only returned if store_date_bounds = TRUE

week_max_hh

Integer. Maximum week position within household (for debugging). Only returned if store_date_bounds = TRUE

ref_month_yyyymm

Integer. Identified reference month in the format YYYYMM, where MM follows the IBGE calendar. 1 <= MM <= 12

ref_fortnight_yyyyff

Integer. Identified reference fortnight in the format YYYYFF, where FF follows the IBGE calendar. 1 <= FF <= 24

ref_week_yyyyww

Integer. Identified reference Week in the format YYYYWW, where WW follows the IBGE calendar. 1 <= WW <= 48

determined_month

Logical. Flags if the month was determined.

determined_fortnight

Logical. Flags if the fortnight was determined.

determined_week

Logical. Flags if the week was determined.

Details

Builds a crosswalk containing reference periods (month, fortnight, and week) for PNADC survey data based on IBGE's interview timing rules.

Temporal Granularity

The crosswalk contains three levels of temporal granularity:

  • Month: 3 per quarter, ~97\

  • Fortnight (quinzena): 6 per quarter, ~9\

  • Week: 12 per quarter, ~3\

Cross-Quarter Aggregation (Important!)

For optimal month determination rates, input data should be stacked across multiple quarters (ideally 4+ years). The algorithm leverages PNADC's rotating panel design where the same UPA-V1014 is interviewed in the same relative position across quarterly visits.

Fortnight Definition

Fortnights are numbered 1-6 per quarter (2 per month), based on the IBGE reference week calendar (not calendar days). Each IBGE "month" consists of exactly 4 reference weeks (28 days), starting on a Sunday:

  • Fortnight 1 in month: IBGE weeks 1-2 (days 1-14 of the IBGE month)

  • Fortnight 2 in month: IBGE weeks 3-4 (days 15-28 of the IBGE month)

Note

Nested Identification Hierarchy

The algorithm enforces strict nesting by construction:

  • Fortnights can ONLY be identified for observations with determined months

  • Weeks can ONLY be identified for observations with determined fortnights

This guarantees: determined_week => determined_fortnight => determined_month

Aggregation Levels

The crosswalk aggregates at different levels:

  • Months: UPA-V1014 level across ALL quarters (PNADC panel design ensures same month position)

  • Fortnights: Household level within quarter only

  • Weeks: Household level within quarter only

See also

pnadc_apply_periods to apply the crosswalk and calibrate weights

Examples

if (FALSE) { # \dontrun{
# Build crosswalk from stacked quarterly data
crosswalk <- pnadc_identify_periods(pnadc_stacked)

# Check determination rates
crosswalk[, .(
  month_rate = mean(determined_month),
  fortnight_rate = mean(determined_fortnight),
  week_rate = mean(determined_week)
)]

# Verify nesting (always TRUE by construction)
crosswalk[determined_fortnight, all(determined_month)]
crosswalk[determined_week, all(determined_fortnight)]

# Apply to a specific dataset
result <- pnadc_apply_periods(pnadc_2023, crosswalk,
                              weight_var = "V1028",
                              anchor = "quarter")
} # }