Shares of Amplitude Inc. opened nearly 43 percent above their reference price in their Nasdaq debut on Tuesday, notching up a valuation of about $5 billion for the benchmark-backed analytics company. San Francisco-based Amplitude, which confidentially filed for a direct listing in July, was valued at $4 billion after raising $150 million from Sequoia Capital and Singapore’s sovereign wealth fund GIC in June. Stock of the company opened at $50 per share, up from the reference price of $35 per share. Amplitude provides data analytics tools that enable companies to optimize their products. Its customers include NBCUniversal, PayPal Holdings Ltd., Peloton Interactive Inc., and Instacart. It has benefited from the accelerated digital transformation during the pandemic, as companies seek to optimize customer experience online by using analytical tools. It reported $72 million in revenue for the first half of the year, a 56 percent jump year over year, compared with …