 For patents, Period 2, the time-varying period, occurred over a span of 10 years (1980-1990), while it was much sharper (3 years) for trademarks (1977-1980).
<clarity>  For patents, Period 2, the time-varying period, occurred over a span of 10 years (1980-1990), while it was much sharper (3 years) for trademarks (1977-1980).
 For patents, the inflection occurred over a span of 10 years (1980-1990), while it was much sharper (3 years) for trademarks (1977-1980).