Update README.md

README.md

@@ -196,6 +196,45 @@ For_a_clear_understanding_of_the_data,_here_is_a_mapping_of_the_IDs_used_in_the_
 | `City_02` | Alborz | `ساوجبلاغ` | Savojbolagh |
 | ... | ... | ... | ... |
 
+
+## Considerations for the Population Dataset of Iranian Cities
+
+### Context
+According to the Cabinet Resolution dated 2020-05-23 (03/03/1399 in the Iranian calendar) regarding the cancellation of the **2021 National Population and Housing Census**, the Statistical Center of Iran undertook the task of **population forecasting at the county level**.
+
+---
+
+### County-Level Population Forecasting Method
+
+1. **Provincial Population Forecast for 2021** using a combined method.
+2. **Reconstruction of the population** from the 2011 and 2016 censuses for the geographic boundaries as of September 2021.
+3. **County population forecasting**:
+   - **a. Share method**: Based on 2016 census results and the projected provincial population using the combined method.  
+   - **b. Mathematical method**: Based on 2011 and 2016 census results and the projected provincial population using the combined method.  
+   - **c. Exponential method**: Based on 2011 and 2016 census results and the projected provincial population using the combined method.  
+   - **d. Average of the three methods** (a, b, c).  
+   - **e. Expert opinion**: Obtaining feedback from provincial experts on population changes at the county level, disaggregated by urban and rural areas.  
+   - **f. Trend analysis**: Reviewing the growth trends of total, urban, and rural populations in the county for the two previous five-year periods based on the reconstructed new boundaries.  
+   - **g. Final synthesis**: Combining all methods to produce an expert-based final county-level forecast.
+
+---
+
+### County-Level Household Forecasting Method
+
+1. **Provincial household forecast for 2021**.
+2. Calculation of **average household size** in 2016 for the reconstructed boundaries.
+3. Calculation of the **2021 household count** using the projected 2021 population and the 2016 household size.
+4. Calculation of the **smoothing coefficient** based on the total number of households from the previous step and the provincial household forecast in step 1.
+5. Calculation of the **final county-level household count for 2021**.
+
+---
+
+**Note:** Differences in total sums are due to estimation and rounding.
+
+---
+
+**Population and household forecasts** are provided separately for **urban and rural areas**, at both **provincial and county levels**, for the year 2021.
+
 ## Usage_Examples
 
 This_dataset_can_be_used_for_various_purposes,_including_but_not_limited_to: