We repurchase $375 million worth of common shares in the first quarter. At present, based on our capital spending plans for the year and subject to market conditions, we still anticipate repurchasing at least $375 million of shares per quarter for the balance of the year consistent with our January guidance. More positive sentiment from clients and markets persisted into the first quarter. Clients increasingly turned to BlackRock to reposition and redeploy across their portfolios. First quarter long-term net inflows of $76 billion were positive across active and index strategies as well as each of our client and product types. ETF net inflows of $67 billion were led by core equity and fixed income ETFs with net inflows of $37 billion and $18 billion respectively.
These inflows were partially offset by seasonal tax trading related outflows from our U.S. style box exposure and precision ETFs. As you will hear from Larry, our Bitcoin IBIT saw surging demand after launching in January, gathering $14 billion of net inflows in the quarter. This is just the latest example of BlackRock’s innovating to provide better access and transparency to a wider range of investment exposures. Retail net inflows of $7 billion were led by continued growth in Aperio as well as renewed demand for active fixed income. Financial advisors are increasingly looking to customize whole portfolios at scale, driving growth across our SMA and managed model platforms. Our partnership with in Envestnet is one channel powering flows through model portfolios.
We saw our best growth sales month ever on the platform and year-to-date organic asset and revenue growth has more than doubled compared to this time last year. Sales on the platform aren’t just accelerating, they are diversifying. We similarly saw record growth flows and custom models and record AUM and our global allocation models both of which have larger active components. Within SMAs, our previously mentioned acquisition of SpiderRock Advisors will further enhance our product offerings and provide even greater personalization across our wealth segments. Institutional active net inflows of $15 billion were driven by our LifePath target date franchise and outsourcing mandates. We see significant momentum across our whole portfolio capabilities.
Our pipeline remains strong as more and more clients turn to BlackRock for outsourcing outflows of $13 billion were concentrated in low fee index equities, as several large clients rebalanced their portfolios amid significant equity market appreciation in the last six months. Our private markets franchise saw $1 billion of net inflows continued demand for our liquid offerings was offset by alpha generation for our clients, reflected in over $3 billion of fund monetization and LP distributions or change in fee basis, primarily for more seasoned private equity solutions programs. Finally, BlackRock’s cash management platform saw $19 billion of net outflows in the first quarter in line with institutional money market industry trends. Our cash business can experience seasonal rotations in the first quarter as many institutional clients withdraw these liquid assets for operational purposes, including tax and bonus payments.
Cash management flows were impacted by approximately $14 billion of net redemptions during the last week of March ahead of the Good Friday holiday. Outflows were driven by clients redeeming balances to have cash on hand during a time when many businesses are open, but the financial markets are closed. This phenomenon is not uncommon or unique to BlackRock. Balance has largely returned with approximately $20 billion of money market net inflows in the first week of April. BlackRock’s differentiated business model has enabled us to continue to grow with our clients driving industry leading organic growth and margins. Looking ahead as markets trend to be more supportive and clients re-risk, we see significant opportunity to expand our market share and consolidate our position with clients.
We’ve set ourselves up to be a structural grower with the diversified platform that we’ve built. Enthusiasm is growing, momentum’s building across the platform. All of us at BlackRock are excited about our future and the growing opportunities for BlackRock, for our clients, for our employees and, of course, for our shareholders. With that, I’ll turn it over to Larry.
Laurence Fink: Thank you, Martin. Good morning, everyone and thank you for joining the call. BlackRock is partnering with clients to navigate structural and secular changes in business models, technology, monetary and fiscal policies, always staying focused on each and every client goal. Through this connectivity, we are having richer conversations with clients than ever before about their whole portfolio and in many cases deepening our relationships with them. This is driving accelerating momentum with a strong pipeline that has some of the best breadth of opportunities across all our client channels and regions that we’ve ever seen. BlackRock’s integrated investment technology advisory platform and durable performance are resonating.
In my conversations with clients around the world, I’m hearing about how they want to put their money to work. But they want to do it differently than they did in the past. They want their portfolios to be more holistically blending public and private markets active in an index. They want their portfolios to be nimble, customized, text-enabled. They want to work with fewer providers or maybe just with one provider. BlackRock is the only asset manager that can partner in this way having the most diverse, integrated investment and technology platform in the industry. Clients around the world are choosing to do more with BlackRock and this is resonating in our results. But I’m actually more excited about the building momentum we’re seeing across our entire platform.
BlackRock’s AUM ended the first quarter at a new record of nearly $10.5 trillion, up $1.4 trillion or 15% over the last 12 months. Also, at that time, BlackRock has entrusted BlackRock with than $236 billion of net new assets. BlackRock generated positive net flows across active and index and across all client types. And we grew our technology service revenues and ACV as clients leverage Aladdin to support investments, processes and in their entire platform. We’ve had a number of real large marquee wins in Aladdin and are working on a number of significant new opportunities. Momentum remains strong as we grow with new and existing clients. We continue to deliver sustained asset and technology services growth at scale. BlackRock’s operating income was up 17% year-over-year and we increased our margin by 180 basis points.
