Background: Innervisions is the 16th studio album by American musician Stevie Wonder, released August 3, 1973, on the Tamla label for Motown Records, a landmark recording of his "classic period". The nine tracks of Innervisions encompass a wide range of themes and issues: from drug abuse in "Too High", through inequality and systemic racism in "Living for the City", to love in the ballads "All in Love Is Fair" and "Golden Lady". The album's closer, "He's Misstra Know-It-All", is a scathing attack on then-US President Richard Nixon, similar to Wonder's song a year later, "You Haven't Done Nothin'".
Context: After Talking Book hit the top 5 of the Billboard albums chart in early 1973 and achieved steady sales during the rest of the year, Innervisions became another considerable hit in the charts. The album debuted on the Billboard albums chart on August 18, 1973 at number 85, then climbed up weekly to number 22, number 14, number nine, number six until reaching its peak position of number four on September 15. The album remained inside the top 20 until the end of the year and remained inside the top 200 during the whole calendar year of 1975. It was also Wonder's second consecutive soul album to top the Black Albums chart where it remained for two weeks. (In the Cashbox chart, Innervisions reached number one near the end of the year.) In the UK the album also achieved success, and became Stevie Wonder's first album ever to reach the UK top 10, peaking at number eight.  Three hit singles were issued from the album. "Higher Ground", released some weeks before Innervisions, reached number four on the singles chart in late October 1973 (it was also a number one on the Cashbox singles chart). "Living for the City" was released immediately and reached number eight in early January 1974. Both singles reached number one on the R&B chart. Finally, "Don't You Worry 'bout a Thing" was released in March, reaching number 16 in early June, and also peaked at number two on the R&B charts. In the UK, "Higher Ground" and "Living for the City" were released as singles but achieved modest success, reaching only numbers 29 and 15, respectively. Only a third single issued there, "He's Misstra Know-It-All", managed to reach the top 10, peaking at number eight on the UK Singles Chart.  "All in Love Is Fair" was a later a hit for Barbra Streisand, who recorded it and released as a single in 1974.
Question: What's the highest point it reached ratings wise?. Whats the answer?
its peak position of number four