Sampling Procedure
Outline of sample design:
A stratified multi-stage design has been adopted for the 67th round survey. The first stage units (FSU) is the census villages (Panchayat wards in case of Kerala) in the rural sector and Urban Frame Survey (UFS) blocks in the urban sector. The ultimate stage units (USU) is enterprises in both the sectors. In case of large FSUs, one intermediate stage of sampling will be the selection of three hamlet-groups (hgs)/ sub-blocks (sbs) from each large rural/ urban FSU.
Sampling frame to be used for selection of first stage units
Census 2001 list of villages is used as the sampling frame for rural areas. Auxiliary information such as number of enterprises, number of workers, type of enterprises, activities of enterprises, etc. available from EC-2005 frame is used for stratification, sub-stratification and selection of enterprises.
In Kerala, list of panchayat wards as per Census 2001 will be used as frame since list of such wards is not available as per EC 2005 frame.
In the urban sector, EC-2005 frame is used for 26 cities with population more than a million as per census 2001. Although Mumbai is a million plus city, EC-2005 frame is not used for Mumbai because of identification problem for IV unit/blocks in the EC for the city. For other cities/towns (including Mumbai), UFS frame (2002-07 phase or latest available phase prior to 2002-07 if it is not available) is used.
Stratification:
Each district is a basic stratum in both rural and urban areas. However, in case of urban, each city with population of 1 million or more as per Census 2001 forms a separate stratum and all other cities/towns of a district is grouped to form another stratum.
Sub-stratification:
(i) Rural: There is three sub-strata in the rural sector:
(1) Villages with at least 5 establishments (NDE/DE) (see para 1.4.17 and 1.4.18 for definition of NDE/DE) under coverage in the manufacturing sector as per EC-2005 information;
(2) Remaining villages having at least 5 NDE/DE under coverage in the services sector including trade as per EC-2005 information;
(3) Remaining villages of the stratum.
For the State(s) where EC-2005 information cannot be used as auxiliary information for stratification/sub-stratification due to limitations of EC 2005 frame, each district is sub-stratified into 'r/4' sub-strata with a sample allocation of 4 per sub-stratum where 'r' is the sample allocation for the district/stratum. The sub-strata is formed by arranging the villages in terms of population so that total population of each sub-stratum is approximately the same.
(ii) Urban, Million plus cities (excluding Mumbai) :
For each stratum / million plus city, 20 sub-strata will be formed as under:
Sub-stratum 1: Blocks with one or more establishment in insurance & pension funding;
Sub-stratum 2: Remaining blocks with one or more establishment in storage & warehousing;
Sub-stratum 3: Remaining blocks with one or more establishment in accommodation;
Sub-strata 4-8: Remaining blocks with one or more establishment in broad activities of manufacturing (as per SSS formation discussed subsequently under para 1.3.10);
Sub-strata 9-12: Remaining blocks with one or more establishment in broad activities of trade (as per SSS formation in para 1.3.10);
Sub-strata 13-19: Remaining blocks with one or more establishment in broad activities of other services (as per SSS formation in para 1.3.10) excluding the activities covered under sub-strata 1-3.
Sub-strata 20: All remaining blocks of the stratum.
(iii) Urban, Other cities and towns (including Mumbai): Two sub-strata is formed:
Sub-stratum 1: UFS block types: Bazaar area (BA)/ Industrial area (IA)/ Hospital area/ (HA)/ Slum area (SA) which are likely to contain relatively higher number of enterprises;
Sub-stratum 2: Remaining UFS blocks of the stratum.
If the number of FSUs in the frame of a rural or urban sub-stratum is found to be less than 8, then separate sub-stratum is formed and it is merged with the adjacent sub-stratum.
There is only one town (Leh) in Leh district and one town (Kargil) in Kargil district of J & K. These two towns are out of UFS coverage. These are treated as sub-stratum 2 and the entire town is treated as one FSU.
Total Sample size (FSUs):
A sample of 16000 FSUs for central sample and 17176 FSUs for state sample have been allocated at all-India level.
Allocation of total sample FSUs:
(i) All-India allocation over States: All-India sample size (FSUs) have been allocated to different State/UTs taking into account the minimum allocations required for a State/UT and the proportion of non-agricultural workers as per EC-2005 in the State/UT.
(ii) State/UT allocation over rural/urban sectors: State/UT sample sizes is allocated to rural and urban sectors of the State/UT in proportion to number of non-agricultural workers as per EC-2005 with the constraint that urban allocation should not be too high compared to rural allocation and both rural and urban allocations is in multiples of 8.
(iii) State × sector allocation over strata: Stratum allocations of State/UT sample sizes for each sector is made in proportion to number of non-agricultural workers as per EC-2005. For the States/UTs where census 2001 frame was used in the rural sector, allocations to strata are made in proportion to population as per census.
(iv) Stratum allocation over sub-strata: Allocations to sub-strata are made:
(a) In proportion to number of non-agricultural workers as per EC-2005 in rural sector as well as in million plus cities (after assuming the number as 1 for those villages/blocks where number of non-agricultural workers is 0);
(b) In proportion to number of blocks with a double weight to sub-stratum 1 for other than million plus cities.
Minimum allocation for a sub-stratum is 4.
Selection of FSUs:
(a) Rural & million plus cities: From each sub-stratum, required number of sample villages/blocks will be selected by probability proportional to size with replacement (PPSWR), size being the number of total non-agricultural workers under coverage in the village/block as per EC-2005.
For the State(s) where EC-2005 information cannot be used as auxiliary information for selection of FSUs due to limitations of EC 2005 frame, size for PPSWR selection is the population of the village as per Census 2001.
(b) Urban (other than million plus cities): From each sub-stratum FSUs are selected by using Simple Random Sampling Without Replacement (SRSWOR). However, for Leh and Kargil towns, each town is selected 4 times, once in each sub-round.
Both rural and urban samples is drawn in the form of two independent sub-samples and equal number of samples is allocated among the four sub rounds.
Formation of segment 9 and selection of hamlet-groups/ sub-blocks
Proper identification of the FSU boundaries: The first task of the field investigators is to ascertain the exact boundaries of the sample FSU as per its identification particulars given in the sample list. For urban samples, the boundaries of each FSU may be identified by referring to the map corresponding to the frame code specified in the sample list (even though map of the block for a latter period of the UFS might be available).
Formation of Segment 9: Having determined the boundaries of the sample FSU, all non-agricultural enterprises having 20 or more workers in the entire FSU and having operated at least one day during last 365 days preceding the day of survey (hereinafter to be called as 'big enterprises') are listed and all the eligible units under coverage are surveyed. All the listed big units (whether under coverage or not) constitute segment 9. All eligible enterprises under coverage were surveyed in segment 9.
Criterion for hamlet-group/ sub-block formation: Having constituted segment 9 as stated above, it is to be determined whether listing is done in the whole sample FSU or not. For this, approximate present population (P) and approximate total number of non-agricultural enterprises (E) for the whole FSU may be ascertained first from knowledgeable persons. Depending upon the values of 'P' and 'E', it is divided into a suitable number (say, D) of 'hamlet-groups' in the rural sector and 'sub-blocks' in the urban sector as stated below. Final value of 'D' is the higher of the two values 'P' and 'E' based on the dual criteria.
While considering enterprise criteria, segment 9 enterprises, if any, may be excluded from the count of 'E', if possible.
For rural areas of Himachal Pradesh, Sikkim, Uttarakhand (except four districts Dehradun (P), Nainital (P), Hardwar and Udham Singh Nagar), Poonch, Rajouri, Udhampur, Doda, Leh (Ladakh), Kargil districts of Jammu and Kashmir and Idukki district of Kerala, the number of hamlet-groups is formed as follows:
population (P) | no. of hgs/ sbs to be formed | no. of non-agricultural enterprises (E) | no. of hgs/ sbs to be formed
less than 600 | 1 | less than 120 | 1
600 - 799 | 4 | 120 - 159 | 4
800 - 899 | 5 | 160 - 199 | 5
1000 - 1199 | 6 | 200 - 239 | 6
and so on | … | and so on | …
Formation and selection of hamlet-groups/ sub-blocks:
In case hamlet-groups/ sub-blocks are to be formed in the sample FSU, the same should be done either by more or less equalizing population or by equalising number of non-agricultural enterprises (details are in Chapter Two). If the criterion for deciding the value of 'D' is population, then hg/sb may be formed by equalising population. On the other hand, if enterprise criterion has been used for deciding 'D', then equlaise the number of non-agricultural enterprises to form 'D' number of hg/sb. If the value of 'D' is same for both population and enterprise criteria, then hg/sb may be formed by equalising population.
Segments 1 & 2: Two segments (in addition to segment 9 already formed) are selected from a large FSU wherever hamlet-groups/ sub-blocks have been formed in the following manner - Segment 1 is the hg/sb having maximum number of establishments under the coverage Two more hg's/sb's is chosen by SRSWOR and combined to form Segment 2.
Listing and selection of the enterprises is done independently in the two selected segments. The FSUs without hg/ sb formation are treated as sample segment number 1.
Listing of households/ enterprises and formation of their frame: Having determined the area(s) to be considered for listing, the next step is to list all the households and non-agricultural enterprises (NAEs) [including those found to be temporarily locked after ascertaining temporariness of locking of NAEs through local enquiry]. Although all non-agricultural enterprises are to be listed, only the unincorporated manufacturing, trade and service sector enterprises which are eligible are covered.
Further, those enterprises which operated for at least 30 days (15 days for seasonal enterprises and SHGs) during the reference year (i.e. last 365 days preceding the date of survey) qualify for survey. Such enterprises hereafter are referred to as 'eligible enterprises'.
Listing and selection of enterprises will be done separately for each of the segments 1, 2 and 9. For segment 2, hg/sb with order of selection number 1 will be listed first and that with order of selection number 2 will be listed next but selection of enterprises will be made from the combined list.
It may be noted that while listing/preparing the frame of enterprises, adequate care should be taken to also list all the enterprises, run by household members, located within the household premises or without fixed premises (like those of mobile vendors). Such enterprises are to be listed against the corresponding households for which visit to every household is necessary to ascertain whether household members own such enterprises
Formation of Second Stage Strata and allocation of enterprises for schedule 2.34:
Nineteen (19) second-stage strata (SSS) are formed within each sample FSU. Composition of various SSS is as under:
(i) 5 SSS considering various broad manufacturing groups were formed in each segment for Manufacturing sector Establishments: (1) SSS 1 - Food products, Beverage and Tobacco Products, (2) SSS 2 - Textiles, Leather, etc. and Cotton ginning, cleaning and baling, (3) SSS 3 - Wood and wood products, paper and paper products, printing and publishing etc & Furniture, (4) SSS 4 - Petroleum Products, chemicals, rubber, metals, metal products, machinery and equipments, etc., and (5) SSS 5 - remaining manufacturing activities.
(ii) 4 SSS were formed in each segment for Trade sector Establishments: SSS 6 comprise the activities of commission agents. Excluding the activities of commission agents, three more SSS will be formed. They are as follows: SSS 7 - Trade and repair of motor vehicles and motor cycles; SSS 8 - other wholesale trade and SSS 9 - other retail trade.
(iii) 7 SSS were formed in each segment for Service sector Establishments (other than trade) corresponding to the following broad activities: SSS 10 - Accommodation & food service, SSS 11 - Transport, storage, information & communication, SSS 12 - Financial & insurance activities, SSS 13 - Real Estate and Renting and Business Activities, SSS 14 - Education, SSS 15 - Human health & Social work, and SSS 16 - Other services.
(iv) 3 SSS were formed in each segment for own account enterprises (OAEs) as follows: SSS 17 - OAEs in Manufacturing, SSS 18 - OAEs in Trade, and SSS 19 - OAEs in Other services.
Selection of enterprises
The number of enterprises to be selected for survey (excluding segment 9) from each FSU × segment × SSS is given below:
enterprise type | sector | SSS number | number of enterprises to be surveyed |
| without hg/ sb formation | with hg/ sb formation (for each segment) |
|manufacturing | 1 | 2 | 1 |
| 2 | 2 | 1 |
| 3 | 2 | 1 |
| 4 | 2 | 1 |
| 5 | 2 | 1 |
| sub-total | 10 | 5 |
|trade | 6 | 2 | 1 |
| 7 | 2 | 1 |
| 8 | 2 | 1 |
| 9 | 2 | 1 |
| sub-total | 8 | 4 |
|services | 10 | 2 | 1 |
| 11 | 2 | 1 |
| 12 | 2 | 1 |
| 13 | 2 | 1 |
| 14 | 2 | 1 |
| 15 | 2 | 1 |
| 16 | 2 | 1 |
| sub-total | 14 | 7 |
OAEs |manufacturing | 17 | 4 | 2 |
|trade | 18 | 4 | 2 |
|services | 19 | 4 | 2 |
|sub-total | 12 | 6 |
It may be noted that from each segment × SSS, at least one enterprise must be surveyed if there are some enterprises in the corresponding frame. In other words, as per the notations used in blocks 5a and 5b of schedule 0.0, e >0 if E >0 for each FSU × segment × SSS.
In addition to the above, all the eligible enterprises of segment 9 were surveyed.
Selection of Enterprises: Sample enterprises from each SSS the are selected by SRSWOR.
However, all the establishments in the frame are selected for a broad category of establishments (manufacturing/trade/other services) in the following situations:
(i) All the manufacturing establishments if total number of establishments in manufacturing SSSs is less than or equal to 10 considering both the segments 1 & 2
(ii) All the trading establishments if total number of establishments in trading SSSs is less than or equal to 8 considering both the segments 1 & 2
(iii) All the 'other service sector' establishments if total number of establishments in other services SSSs is less than or equal to 14 considering both the segments 1 & 2.