Table B-1. Unweighted and base-weighted response rates by stage of data collection by wave and type of weighting: 2007–08 through 2009

Table B-1. Unweighted and base-weighted response rates by stage of data collection by wave and type of weighting: 2007–08 through 2009–10
Response rate	BTLS wave	2007–08 SASS Teacher Listing Form	2007–08 SASS public school teachers with 1 to 3 years of experience	Overall response rate
First wave
Unweighted	†	86.7	84.6	73.4
Base-weighted	†	86.2	84.3	72.7
Second wave without retrospective cases
Unweighted	84.7	86.7	84.6	62.1
Base-weighted	84.5	86.2	84.3	61.4
Second wave with retrospective cases
Unweighted	91.8	86.7	84.6	67.4
Base-weighted	91.9	86.2	84.3	66.8
Third wave
Unweighted	86.2	86.7	84.6	63.3
Base-weighted	86.1	86.2	84.3	62.5
† Not applicable.
NOTE: Retrospective cases are respondents that were non-interviews during the second wave, but provided replies to second wave items during the third wave. Base-weighted response rates use the inverse of the probability of selection and the sampling adjustment factor.
SOURCE: U.S. Department of Education, National Center for Education Statistics, Beginning Teacher Longitudinal Study (BTLS), "First Through Third Wave Preliminary Data File, 2007–08, 2008–09, 2009–10".