Mind the Mode: IVR vs SMS in Zimbabwe


It’s all in the mode. Or is it? Would your response over the phone be different than when you had a person in front of you asking a question? When answering a question over the phone would you respond differently if you were speaking to a friendly operator or a recorded voice or were replying by SMS? These are pretty key considerations when you are in the business of asking people questions from afar, and we get asked about it a lot.

So, welcome to our first edition of our ‘Mind the Mode’ Series. We have been conducting some mode experiments to find out whether people respond differently to different survey modes: live calls, IVR (Interactive Voice Response- that recorded voice asking you to press 1 for English or 2 for Spanish), SMS, or face-to-face. In this first edition, we look at IVR and SMS in Zimbabwe.

You might never have thought about it before, but it turns out that IVR and SMS compete. In the automated data collection space, there are two schools of thought: one favors data collection via SMS, the other IVR. The SMS advocates argue that a respondent can take the survey at the time of their choice and at their pace. Proponents of IVR point to the fact that voice recordings are easier to understand than a text message because you don’t need to be literate to take the survey. It’s therefore the more ‘democratic’ tool.

At mVAM, we’ve mostly been using SMS but in Zimbabwe, we had the opportunity to compare these two modes. Food security data was collected by both SMS and IVR in August 2016. IVR responses were received from 1760 randomly selected respondents throughout Zimbabwe and 2450 SMS responses were received from a different set of random respondents stratified by province. Most responses came from Manicaland, Harare, Masvingo and Midlands for both types of surveys due to higher population densities, better network coverage and higher phone ownership in these areas.

Respondents were asked pretty similar questions in both surveys. Both surveys asked:

  • demographic and location questions such as the age and gender of the respondent, the gender of the head of household, and the province and district that they lived in
  • type of toilet in their house (to gain a rough estimate of socio-economic status);
  • daily manual labour wage and
  • whether they used any of the five coping strategies (a proxy for food insecurity
  1. Rely on less preferred or less expensive food due to lack of food or money to buy food?
  2. Borrow food, or rely on help from a friend or relative due to lack of food or money to buy food?
  3. Reduce the number of meals eaten in a day due to lack of food or money to buy food?
  4. Limit portion sizes at mealtime due to lack of food or money to buy food?
  5. Restrict consumption by adults so children could eat

However, there were a few aspects where the surveys were slightly different. The SMS survey gave an incentive of USD 0.50 airtime credit to respondents who completed the survey whilst there was no incentive to do the IVR one. In the IVR survey, respondents could choose between English or Shona (most respondents chose to take it in Shona) whereas the SMS survey was only conducted in English.

So, what have we learned?

IVR and SMS reach different demographics.

Our IVR and SMS surveys reached different demographics. A higher proportion of IVR responses came from the worse-off households, i.e. those with no toilets or with pit latrines compared to SMS responses. Similarly, a higher proportion of households headed by women participated in the IVR survey than the SMS survey. WFP generally finds that households headed by women usually are more food insecure. So IVR surveys appear have greater reach to worse-off households. This may be because they do not require literacy or knowledge of Englishas with SMS surveys.


Fig. 1a: IVR respondents by toilet type


Fig. 1b: SMS respondents by toilet type


Fig. 1c: IVR respondents by head of household sex


Fig. 1d: SMS respondents by head of household sex

IVR surveys give higher food insecurity estimates than SMS. Spoiler: The reason is unclear.

In general, we found that IVR responses showed higher coping levels than SMS responses. The mean reduced coping strategy index (rCSI) is used as a proxy for food insecurity. A higher rCSI means people have to cope more in response to lack of food or money to buy food, meaning they are more food insecure. In Zimbabwe, mean rCSI captured through IVR (21.9) was higher than that captured through SMS (18.3) for the entire country. This difference in mean rCSI was consistent across cross-sections by the sex of the household head and by province (Figs. 2 and 3).


Fig. 2: rCSI by sex of household head


Fig. 3: Mean rCSI by province

However, when the data was analysed by toilet type, which was used as the proxy indicator for wealth, we saw a slightly different pattern. Flush toilets are considered as a proxy for the best-off, followed by Blair pit latrine (a ventilated pit latrine), then pit latrine and then no toilets. We also asked about composting toilets but too few households had them to make any meaningful comparisons. The mean rCSI was only significantly different for households with flush toilets and with pit latrines (in both cases IVR responses had higher rCSI). The mean rCSI results for the other two toilet categories (Blair pit latrine and no toilet) were not significantly different in the two types of surveys. Therefore, the commonly observed difference between IVR and SMS responses is not observed across all wealth groups (Fig. 4).


Fig. 4: rCSI by toilet type

This suggests that the higher overall mean rCSI in IVR respondents compared to SMS respondents is not be coming from the fact that IVR reached more worse off households. However, we say this with a big caveat. Toilet type as we said above is a rough indicator and it might not be an accurate indication of which households are worse off. It’s possible that we would have seen different results if we had used a different type of proxy indicator for wealth groups.

When we examine this a bit further and break down the rCSI into the individual coping strategies in Figure 5, we see that IVR respondents use more coping strategies more frequently than SMS respondents. This make sense because the individual coping strategies are what are used to calculate the rCSI and we already observed higher mean rCSI in IVR respondents.


Fig. 5: Percentage of households using different coping strategies

However, we also noticed something else when looking at responses to each coping strategy. There is a much higher variation in coping strategy use within SMS respondents compared to IVR respondents (see Figure 5). This suggests that respondents may be ‘straightlining’, i.e. providing the same response to every question. Straightlining suggests that people just don’t respond well to a recorded voice over the phone. While SMS is not good for literacy reasons, it does give the respondent more control over the pace of the survey. With SMS, respondents have as much time as they want to read (or re-read) the whole text and respond. With IVR, people have to go at the speed of the questions. They could get impatient waiting to hear all the answers to a question or they might not have enough time to understand the question. In both cases, they might just start pressing the same answer to get to the next question. Thus IVR might not give quality results.

Interestingly, we saw a similar pattern in Liberia during the Ebola epidemic. We used both SMS and IVR to collect information during the emergency. IVR results showed very high rCSI with limited variation. SMS data consistently produced lower (and more credible) rCSI estimates, and the variation in the data was greater (perhaps a sign of greater data quality).

Different demographics or differences in user experiences (i.e. straightlining) could be contributing to different food security estimates in IVR and SMS.

The upshot is that different survey tools lead to different results, and we need to understand these differences as the use of automated mobile data collection expands. We are not sure whether the different demographics among IVR and SMS respondents are the cause of higher food insecurity estimates for IVR or whether the different user experiences are in play, especially that IVR respondents may be straightlining their answers and not accurately reflecting their coping levels. We suspect that a bit of both might be in play.

Stay tuned for the next editions of our ‘Mind the Mode’ series as we continue to document our learning on the mode experiments

Originally published at MVAM: THE BLOG.

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