a, Raw data of the number of transcripts measured by our methods. Each dot (gray) in the plot is one measurement from a single TAS. The number of TAS measured is 3,010 for Gli1 (and 1,289 for RG6 in Supplementary Fig. 2). Geometric means are shown in orange or pink or blue. Error bars represent standard error of the mean. b, On the basis of a, we find splicing efficiency (1–N1/NE1 or 1–N1/NE2) increases with transcription level (orange and pink), while control (1–NE1/NE2 or 1–NE2/NE1) measurements remained constant (blue). Solid lines are guides to the eye to highlight the ‘economy of scale’ behavior. Geometric means are shown in orange or pink or blue. Error bars represent standard error of the mean. The ‘economy of scale’ mathematical model is discussed in the main text. c, Overlapped curves from b. d, Overlapped curves of the synthetic gene RG6. e, Overlapped curves from biological repeats for Gli1 and RG6. All of them showed the repeatability of ‘economy of scale’ observation. Source data are available online.