Experiments to convert 

partials to completes

Vanessa Harrell1, Margie Engle Bauer1, 

Todd Hughes2, Jiangzhou Fu2

FCSM 2023 1 SSRS 

2 UCLA
Challenges of Mail-Push-to-Web

ssrs.com | @ssrs_research | 2

• A number of state Health Interview Studies (HIS) rely on Mail-Push-to-Web methodologies

• Unlike phone interviews, partially completed interviews are more common on the web 

– Often accounting for 20%-30% of interviews that are started

• What constitute a partial? 

– Anywhere from one question answered to most questions answered

– Study specific

• For these cases, reminders were either not successful or not existent (depending on when the 

respondent started the interview)

• Why did respondents break off?

– Dissatisfied with survey content

– Dissatisfied with a specific question

– Lack of time

– Loss of interest
Background

ssrs.com | @ssrs_research | 3

• We started looking into partials for CHIS, due to an increase in 2021

• We noted some demographics differences:

– Lower education

– More Hispanic

– More uninsured

– More cell phone

• Important demographics that are often harder to reach
Research Questions?

ssrs.com | @ssrs_research | 4

• What can motivate these respondents to complete their interview?

– Communication?

– Pre-incentive?

– Post-incentive?

• Is the cost of trying to convert a partial lower than getting a complete from fresh sample?
Study #1 - CHIS

ssrs.com | @ssrs_research | 5

• The California Health Interview Survey (CHIS) is the largest state health survey in the nation. It 

is a leading source of credible and comprehensive data on the health and health care needs of 

California’s large and diverse population

• It is conducted for the UCLA Center for Health Policy Research (CHPR)

• It is fielded every year

• 20,000 adult completes from ABS in 2023

• Mail push-to-web with 4 contacts and phone follow up

– Invitation letter, with a visible pre-incentive

– +2 weeks, Reminder postcard 

– +4 weeks, Reminder letter

– +6 weeks, Reminder postcard

– +8 weeks, Outbound phone call (matched phone numbers)
Study #2 - MHIS

ssrs.com | @ssrs_research | 6

• The Massachusetts Health Insurance Survey (MHIS) aims to document health insurance 

coverage, access to and use of health care, and health care affordability for the 

noninstitutionalized population in Massachusetts 

• It is conducted every two years

• It is conducted for the Center for Health Information and Analysis (CHIA)

• 4,400 ABS completes in the 2023 cycle

• Mail push-to-web with 4 contacts

– Invitation Letter, with a visible pre-incentive

– +1 week, Reminder postcard

– +3 weeks, Reminder letter

– +4 weeks, Reminder postcard
ssrs.com | @ssrs_research | 7

The Experiments

CHIS

• Qualified as Partials if screener and section A 

(demos) were completed

– Also included “Sufficient Partials"

• 3 Conditions:

– No intervention

– Letter only

– Letter with $10 promised post-incentive

 $10 gift card

• Letter sent in English or bilingual with 

language used to start the survey

MHIS

• Qualified as Partials if at least one question of 

the survey was started

• 3 Conditions:

– Letter only

– Letter with $10 promised post-incentive

– Letter with $10 promised post-incentive 

and $2 visible cash pre-incentive

 $10 e-gift card

• Letter sent in English or bilingual 

English/Spanish depending on the language 

used to start the survey
ssrs.com | @ssrs_research | 8

The CHIS Letter
ssrs.com | @ssrs_research | 9

The MHIS Letter
ssrs.com | @ssrs_research | 10

Results

% Converted

No Intervention Letter Only Letter with $10 

post-incentive

Letter with $10 

post-incentive 

and $2 preincentive

CHIS* 1.8% 8.4% 5.4%

MHIS 6.5% 8.8% 16.4%

* Preliminary results
ssrs.com | @ssrs_research | 11

Results (CHIS)

Printing, Postage, Incentive Costs per Complete

Printing Pre-incentive Postage Post-incentive Cost per 

Complete

CHIS – normal 

protocol* $10.23 $31 $35.96 - $77.19

CHIS – partial 

conversion, 

letter only*

$11.32 - $6.51 - $17.83

* Preliminary results
ssrs.com | @ssrs_research | 12

Results (MHIS)

Printing, Postage, Incentive Costs per Complete

Printing Pre-incentive Postage Post-incentive Cost per 

Complete

MHIS –

normal 

protocol

$6.78 $10.29 $23.25 - $40.32

MHIS – partial 

conversion, $2 

pre-incentive 

+$10 postincentive

$1.51 $6.10 $3.54 $10 $21.15
ssrs.com | @ssrs_research | 13

Conclusions

• CHIS – Results are puzzling

– We did not expect a huge increase with the $10 post-incentive due to having to open 

the envelope, but certainly did not expect less

• MHIS – visible cash did help

• Overall conversion is much cheaper

• Quicker to obtain completes
Limitations

ssrs.com | @ssrs_research | 14

• Conversion letters were sent in batches after the standard protocol was exhausted

– Mix of respondents being contacted soon after break off or 2 month later

• Ideal scenario would be to determine a time after break off where a respondent moves to the 

partial conversion protocol

– More challenging from an implementation standpoint

– Impact cost
Future Research

ssrs.com | @ssrs_research | 15

• CHIS study

– Replicate

– Do qualitative

• Look at the impact of the timing of the partial conversion letter on the outcome

• Did the level of completion impact the outcome

• Currently in the field with another HIS

• Protocol

– $2 visible pre-incentive

– Experimenting with the amount of post-incentive

 $5

 $10

• Do the people who break off and resume differ from...

– those who do not break off?

– those who despite our efforts do not resume?
Thank you!

vharrell@ssrs.com
Survey respondents invited by mail to complete a web survey sometimes start a survey but fail to complete it for a variety of reasons, 

resulting in a breakoff. While some respondents may not be willing to resume due to disapproval of the survey content or a particular 

question, it is safe to assume that others break off for a variety of other reasons, such as lack of time or loss of interest. Since these 

respondents read our materials and started the survey initially, we believe that offering incentives may help convert these surveys to 

completes, at a lower cost than releasing additional sample. 

In this presentation, we will delve into experiments that we conducted on two health surveys – the California Health Interview Survey 

(CHIS) and the Massachusetts Health Insurance Survey (MHIS) – for converting partial surveys to completed surveys. Specifically, we will 

assess the impact of a letter, a pre-incentive, and a promised post-incentive in converting partials to completes.