Table 3 Alternative sampling methods in Italy and Spain

Snowball

K stages

Useful for pilot survey

Choice of initial list

Attrition rates

The probability of inclusion is unknown

Full network connectivity assumption

ITA

Interuniversity survey on “Foreigner Immigration to Italy”

Respondent driven sampling

Each municipality was divided into four areas, and one eligible immigrant was selected in each of them. First respondents in each area were not allowed to know each other to avoid overlapping networks; and each respondent could provide up to three contacts for other immigrants who had never lived in the same household as the respondent. The procedure was repeated until the final number of questionnaires was achieved.

over-representation of men, especially in the age group 30-39

SPA

Romanian Communities in Spain, 2008. Four municipalities in the region of Madrid. (Sandu, 2009)

Residential units method (unità abitative)

2 stages

List of apartments with at least a foreigner (1° level unit); random selection of one foreigner (2° level units).

The initial list is updated through snowball question.

Lower non-response rate

Not suitable in big cities

High attrition rate (snowball component)

ITA

Casacchia & Strozza (1990)

Natale & Strozza (1997)

Quota sampling

Quotas by age and gender in 4 Italian Regions.

Selection channels: from contacts obtained in Senegal, or public spaces, migrant associations, snowballing, interviewers’ contacts

Multiple steps with high sample attrition and (non-random) selection

selection biases at origin

ITA & SPA (partial sample)

MAFE 2008.

Beauchemin & González-Ferrer (2011)

Random routes

3 regions with largest percentages of the targeted population

Districts where more than 10% of the population belonged to the target population

To select the final respondents, random routes were combined with a spatial sampling method (see below)^a

age distribution and the average length of stay of the surveyed population was quite similar to the Padrón distribution

women were seriously under-represented in most origin groups

SPA

Remittances of Latin-American immigrants in Spain 2012. Adult immigrants from six Latin American countries

(Izaguirre Vizcaya, et al., 2016).

Spatial sampling (and random routes)

Sampling in centres of aggregation: immigration information offices, public spaces in neighbourhoods and, above all, the queue outside the Moroccan consulate

refusal rates were low – especially among the individuals who were queuing for long hours outside the consulate premises

often the inability to locate anyone in certain public spaces required changing the intersection points

SPA

Localmultidem 2006^b

(Morales & Ros, 2013).

Centre sampling technique

2 stages

List of centre of aggregation (1° level unit); casual selection of one foreign (2° level units).

Non response rate due only to refusal

Suitable also to big cities

Cost-efficient method

Sample more representative and with weighted probabilities

Target population “present population”

Use a shorter questionnaire

ITA

Regional surveys:

Lombardy Regional survey every year since 2001

National surveys:

South survey aimed at studying effects of the 2003 regularization (Blangiardo & Farina, 2006)

Integrometro survey aimed at gathering information on the integration process (Cesareo & Blangiardo, 2009).

PER.La survey, to analyze the working trajectories of the migrant population (Ismu, Censis and Iprs, 2010).

International surveys:

Italian sample in the “Push and Pull factors” (Birindelli, et al., 2000) in the Italian, Portuguese, and Hungarian samples of the “Immigrant Citizens Survey” (Huddleston & Tjaden, 2012); in the sample of Milan for the Localmultidem survey (Morales & Pilati, 2014).