Table:
| ($ in millions) |  |  | Percent |
| --- | --- | --- | --- |
| For the year ended December 31: | 2019 | 2018 | Yr.-to-Yr. Percent Change |
| Licensing of intellectual property including royalty-based fees | $367 | $723 | (43.2)% |
| Custom development income | 246 | 275 | (10.5) |
| Sales/other transfers of intellectual property | 34 | 28 | 22.6 |
| Total | $648 | $1,026 | (36.9)% |
Paragraphs:
Intellectual Property and Custom Development Income
Licensing of intellectual property including royalty-based fees decreased 49.2 percent in 2019 compared to 2018. This was primarily due to a decline in new partnership agreements compared to the prior year. The timing and amount of licensing, sales or other transfers of IP may vary significantly from period to period depending upon the timing of licensing agreements, economic conditions, industry consolidation and the timing of new patents and know-how development.
Question:
What caused the decrease in Licensing of intellectual property?
Answer: This was primarily due to a decline in new partnership agreements compared to the prior year. The timing and amount of licensing, sales or other transfers of IP may vary significantly from period to period depending upon the timing of licensing agreements, economic conditions, industry consolidation and the timing of new patents and know-how development.