Zanata have extensive api which you can use to gather stats:

To get a list of contributors over a period of time for a project version:

https://zanata.ci.cloudbees.com/job/zanata-api-site/site/zanata-common-api/rest-api-docs/resource_ProjectVersionResource.html#resource_ProjectVersionResource_getContributors_GET

To get the stats for a particular individual:

https://zanata.ci.cloudbees.com/job/zanata-api-site/site/zanata-common-api/rest-api-docs/resource_StatisticsResource.html#resource_StatisticsResource_getContributionStatistics_GET

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Alex Eng