Before revision:  A second period started with the creation of the Royal Spanish Academy in 1713, which produced a global standardization process that enforced the official spelling of -ra and -se as perfectly interchangeable variants ( 6) . Time series extracted from a massive corpus of books ( 7) show that this standardization produced a boost in the declining old form -se that eventually faded, leaving -ra  as the dominant one in the present time.
After revision:  A second period started with the creation of the Royal Spanish Academy in 1713, which enforced the spelling of both forms as perfectly interchangeable variants ( 6) . Time series extracted from a massive corpus of books ( 7) show that this standardization produced a boost in the declining old form -se that eventually faded, leaving -ra as the dominant one in the present time.