<prompt> Translate the following text to EnglishKwa kweli, ukuaji ulikuwa wa kasi zaidi katika vipindi fulani - miaka ya 1950 na 1960, na nusu ya pili ya miaka ya 1990 - na polepole zaidi katika vipindi vingine - miaka ya 1970.  <response>: Of course, growth was faster during some periods-the 1950s and 1960s, and the second half of the 1990s-and slower during other periods-the 1970s. 