Could you provide some information on the main quantitative data formats?

SPSS

This is the most popular dissemination format. The SPSS files are either in (.sav) format for newer studies (processed from 2005 onwards) or may be in SPSS portable (.por) format for older studies. SPSS portable and system files open in all current versions of SPSS.

Stata

Stata is increasingly popular and is recommended for surveys that require weighting and other survey design effects to be incorporated into any analyses.

R

An open source statistical package, R is gaining popularity as it offers advanced functionality not present in SPSS or Stata. Depending on the version of SPSS, Stata and R used, R will read both SPSS and Stata formats (using the 'read.spss' and 'read.dta' commands).